At mySMTP, we know that getting your emails delivered to the inbox is crucial for your communication success. Good deliverability doesn’t happen by chance—it requires the right setup, authentication (SPF, DKIM, DMARC), and smart sending habits. We guide you through best practices, from building clean lists to following sending policies, so your messages reach your audience safely, reliably, and with maximum impact.

How to Improve Email Deliverability

Ensuring high email deliverability is essential for maximizing the effectiveness of your email campaigns. When using mySMTP, implementing the right strategies can help ensure your emails reach inboxes instead of spam folders. Here are key strategies to improve your email deliverability:

1. Authenticate Your Emails

Proper authentication helps prevent your emails from being marked as spam. Implement the following authentication methods when using mySMTP:

• SPF (Sender Policy Framework): Authorize mySMTP’s mail servers to send emails on your behalf.
• DKIM (DomainKeys Identified Mail): Digitally sign your emails using mySMTP's record to verify authenticity and build trust with ISPs.
• DMARC (Domain-based Message Authentication, Reporting, and Conformance): Set policies for handling unauthorized emails and monitor reports via mySMTP's DMARC monitoring features.

2. Use a Dedicated IP Address

If you send a high volume of emails, consider using a dedicated IP address through mySMTP to maintain a strong sender reputation. This prevents your email reputation from being affected by other senders sharing an IP.

3. Warm Up Your IP

Gradually increase your sending volume over time to build a positive reputation with ISPs. mySMTP provides guidance on IP warm-up strategies and recommended sending limits.

4. Maintain a Clean Email List

Regularly clean your email list to remove inactive, invalid, or non-engaging recipients. mySMTP offers email verification tools to help ensure your list remains clean and effective. Use double opt-in features provided by mySMTP's MailWizz to confirm subscriber intent.

5. Monitor Blacklists and Reputation

Check your sending domain and IP against blacklists (e.g., Spamhaus, Barracuda) using mySMTP’s monitoring tools. Additionally, track your sender reputation with Google Postmaster Tools and mySMTP analytics.

6. Optimize Email Content

• Avoid spam-triggering words (e.g., "free money," "guarantee").
• Use a proper text-to-image ratio to enhance readability.
• Ensure emails are mobile-friendly and properly formatted to comply with mySMTP’s recommended best practices.

7. Set Up Feedback Loops (FBLs)

Register for feedback loops with major ISPs through mySMTP’s FBL integration to monitor complaints. Remove recipients who mark your emails as spam to maintain a positive sender reputation.

8. Monitor Bounce Rates with mySMTP Analytics

High bounce rates can harm your sender reputation. mySMTP helps classify and handle bounces appropriately:

• Hard Bounces: Remove permanently undeliverable addresses.
• Soft Bounces: Retry sending later, but use mySMTP’s analytics to identify and remove addresses that repeatedly bounce.

By implementing these best practices with mySMTP, you can enhance your email deliverability, ensuring that your messages reach inboxes effectively.

The Importance of DNS Setup for Email Authentication

DNS (Domain Name System) plays a crucial role in email authentication, ensuring that your emails are trusted, secure, and successfully delivered. Without a proper DNS setup, your emails may be flagged as spam, rejected, or even exploited by attackers.

Here’s why DNS configuration is essential for email authentication:

DNS as the Foundation of Email Authentication

Email authentication methods—SPF, DKIM, DMARC, and BIMI—all rely on DNS TXT records to verify your email-sending identity. These records help email providers identify legitimate senders and block malicious attempts (e.g., phishing and spoofing attacks).

Understanding IP Reputation in Shared and Dedicated IPs

IP reputation is a critical factor in email deliverability, directly influencing whether emails land in the inbox, spam folder, or get blocked entirely. Whether using a shared or dedicated IP, understanding how IP reputation is built and maintained is essential for successful email campaigns. This guide provides a deep dive into IP reputation, the pros and cons of shared and dedicated IPs, and best practices to ensure optimal deliverability.

What is IP Reputation?

IP reputation refers to the credibility of an IP address as assessed by Internet Service Providers (ISPs) and spam filters. A positive reputation leads to high deliverability, while a poor reputation results in emails being flagged as spam or rejected. Reputation is based on factors such as sending history, spam complaints, and engagement rates.

Key indicators of IP reputation include:

• Sender Score: A numerical rating (0-100) indicating the trustworthiness of an IP address.
• Blacklist Status: IPs listed on blacklists (e.g., Spamhaus, Barracuda) face deliverability issues.
• Spam Complaints: High complaint rates negatively impact reputation.
• Bounce Rate: Frequent hard bounces suggest poor list quality and damage reputation.
• Engagement Levels: Higher open and click-through rates improve IP credibility.

Shared vs. Dedicated IPs

Shared IPs

• Used by multiple senders, meaning the reputation is influenced by all users of the IP.
• Ideal for businesses with low or inconsistent email volumes.
• Benefits from an established reputation, especially for new senders.
• Managed by mySMTP to ensure compliance with email best practices and prevent abuse.
• More cost-effective, as multiple businesses share the infrastructure.
• Risks: Can be affected by other senders' bad practices, leading to reputation fluctuations.

Dedicated IPs

• Exclusively used by a single sender, meaning reputation is built solely on their sending behavior.
• Best for businesses with high email volumes (e.g., 100,000+ emails per month) and consistent sending patterns.
• Requires proper warm-up strategies to establish a positive reputation before sending large volumes.
• Provides greater control over deliverability, sender identity, and branding.
• Risks: A poor sending strategy (e.g., sudden spikes, high bounce rates) can quickly damage reputation, making recovery difficult.

When to Use a Shared or Dedicated IP

Use a Shared IP if:

• You send fewer than 100,000 emails per month.
• Your sending volume is inconsistent (e.g., seasonal campaigns).
• You are a small business or new sender looking for a trusted sending environment.
• You prefer a cost-effective option without the need for IP warm-up and reputation management.

Use a Dedicated IP if:

• You send high volumes of emails consistently.
• You want full control over your sender reputation.
• You need better brand recognition with custom authentication settings (SPF, DKIM, DMARC).
• You are in a regulated industry (e.g., finance, healthcare) and require stricter security and compliance.

How to Maintain a Strong IP Reputation

To ensure a positive IP reputation and maximize email deliverability, follow these best practices:

• Authenticate Emails: Implement SPF, DKIM, and DMARC to improve credibility.
• Warm Up Dedicated IPs: Gradually increase sending volume to build ISP trust.
• Monitor Performance: Regularly check sender scores, blacklist status, and engagement metrics.
• Maintain List Hygiene: Remove invalid addresses and inactive subscribers to reduce bounce rates.
• Follow Compliance Guidelines: Adhere to GDPR, CAN-SPAM, and other regulations to avoid complaints.
• Engage with Recipients: Send relevant, high-quality content to encourage positive engagement.
• Use a Reputable ESP: mySMTP actively monitors shared and dedicated IPs to ensure high deliverability rates.

IP reputation is a key factor in email success. Shared IPs offer reliability and affordability for smaller senders, while dedicated IPs provide control and branding benefits for high-volume senders. Regardless of the IP type, maintaining best practices ensures a strong reputation and improved inbox placement. mySMTP helps businesses navigate these choices, providing expert management and monitoring for optimal email performance.

mySMTP Blacklist Monitoring and Delisting

Overview

Blacklist monitoring is essential for ensuring high email deliverability. If an IP address or domain associated with mySMTP is blacklisted, outgoing emails may be marked as spam or rejected. Regularly monitoring and delisting from blacklists helps maintain a good sender reputation.

Checking IP Reputation

To check if an IP address or domain is blacklisted, you can use the following tools:

1. MultiRBL (https://multirbl.valli.org/)

• Checks multiple real-time blacklists (RBLs) at once.
• Provides details on why an IP/domain is blacklisted.

2. MXToolbox (https://mxtoolbox.com/blacklists.aspx)

• Offers a blacklist lookup and detailed reputation analysis.
• Includes monitoring alerts for proactive blacklist checks.

3. Spamhaus (https://check.spamhaus.org/)

• Checks IPs against the Spamhaus Block List (SBL), Exploits Block List (XBL), and Policy Block List (PBL).
• Provides reasons and removal instructions if listed.

4. Talos Intelligence (https://talosintelligence.com/)

• Maintains IP reputation scores based on global email activity.
• Identifies if an IP is flagged as suspicious or malicious.

5. Barracuda Reputation System (https://www.barracudacentral.org/lookups)

• Checks if an IP is listed on Barracuda’s blacklist, which affects spam filters globally.

Steps for Delisting

If an IP is found on a blacklist, follow these steps:

1. Identify the Cause
   • Review recent email activity to determine if spam-like behavior occurred.
   • Check if compromised credentials, high bounce rates, or spam complaints contributed to the listing.
2. Follow Removal Procedures
   • Each blacklist provider has a specific removal process, usually involving submitting a request via their website.
   • Some blacklists automatically remove IPs after a period of good behavior.
3. Implement Preventive Measures
   • Set up SPF, DKIM, and DMARC records correctly.
   • Regularly monitor email sending patterns.
   • Use dedicated IPs for bulk email sending.
   • Ensure mailing lists are clean and opt-in based.
4. Monitor and Test
   • Use monitoring services to receive alerts when an IP is blacklisted.
   • Test email delivery to ensure messages are reaching inboxes and not spam folders.

Additional Resources

• Google Postmaster Tools (https://postmaster.google.com/) – Provides sender reputation insights for Gmail.
• Microsoft SNDS (https://postmaster.live.com/) – Helps monitor IP reputation with Microsoft email services.
• mySMTP Support – If issues persist, contact mySMTP support for assistance with delisting and reputation management.

Conclusion

Regular blacklist monitoring and proactive management of IP reputation are crucial for maintaining high deliverability rates. By using the right tools and following best practices, mySMTP users can ensure optimal email performance and avoid disruptions caused by blacklisting.

Handling Bounces and Complaints

Understanding Bounces

Bounces occur when an email fails to be delivered to the recipient. mySMTP categorizes bounces into two main types:

Hard Bounces

A hard bounce indicates a permanent delivery failure. Common reasons include:

• The recipient’s email address does not exist
• The domain of the recipient is incorrect
• The recipient’s email server has blocked delivery

Hard bounces should be removed from mailing lists immediately to maintain sender reputation and avoid deliverability issues.

Soft Bounces

A soft bounce is a temporary delivery failure, typically due to:

• The recipient's mailbox being full
• The recipient's mail server being temporarily down
• The email message being too large

Soft bounces can be retried a few times before being treated as a hard bounce if delivery remains unsuccessful.

Managing Suppression Lists

A suppression list helps prevent emails from being sent to addresses that have previously bounced, complained, or unsubscribed. mySMTP maintains suppression lists to improve email deliverability and compliance.

Automatic Suppression

mySMTP's MailWizz adds email addresses to the suppression list when:

• A hard bounce occurs
• A recipient submits a complaint (via feedback loops with email providers)
• A recipient unsubscribes

Manual Suppression

Users can manually add email addresses to the suppression list to prevent sending unwanted emails.

Handling Complaints

When a recipient marks an email as spam, it is considered a complaint. mySMTP integrates with feedback loops (FBLs) from major email providers to detect complaints.

Reducing Complaints

To minimize complaints:

• Ensure recipients have explicitly opted in to receive emails
• Use a recognizable sender name and email address
• Provide a clear and easy-to-use unsubscribe link
• Avoid excessive or irrelevant emails

Monitoring and Best Practices

Regularly monitor bounce and complaint reports within mySMTP’s dashboard to maintain a high sender reputation. Follow best practices:

• Clean email lists periodically to remove inactive or invalid addresses
• Segment email lists to send targeted and relevant content
• Use authentication protocols like SPF, DKIM, and DMARC to improve email deliverability

By proactively managing bounces and complaints, users can maximize the effectiveness of their email campaigns while maintaining a strong sender reputation.

Email deliverability is the cornerstone of successful email marketing and transactional communications. One of the most critical—yet often overlooked—aspects of maintaining high deliverability rates is proper IP warming. This comprehensive guide explains what IP warming is, why it matters, and how to implement it successfully using the mySMTP Warmup Schedule Generator.

Whether you’re launching a new dedicated IP address, recovering from deliverability issues, or scaling your email operations, this guide will provide you with the knowledge and tools needed to build a strong sender reputation with Internet Service Providers (ISPs) and email receivers.

1. Understanding IP Warming

1.1 What is IP Warming?

IP warming is the practice of gradually increasing the volume of email sent from a new or ‘cold’ IP address over a period of time. This systematic approach allows ISPs and mailbox providers to recognize your IP address as a legitimate sender and build trust in your sending practices.

When you send email from a new IP address without warming it up, ISPs have no historical data about your sending behavior. This makes them cautious, and they may filter your emails to spam folders, throttle delivery, or even block your messages entirely.

1.2 Why IP Warming Matters

The importance of IP warming cannot be overstated. Here’s why it’s critical for your email success:

• Establishes Sender Reputation: ISPs use reputation systems to determine whether your emails should reach the inbox. A gradual warmup demonstrates responsible sending behavior.
• Prevents Blacklisting: Sudden high-volume sending from a new IP triggers spam filters and can result in immediate blacklisting.
• Maximizes Deliverability: Proper warming ensures your emails reach the inbox rather than spam folders, directly impacting your ROI.
• Builds Long-term Success: A well-warmed IP creates a foundation for sustainable, high-volume email sending.

Studies show that properly warmed IP addresses can achieve inbox placement rates of 95% or higher, while unwwarmed IPs often see rates below 50% in the first weeks of sending.

1.3 How ISPs Evaluate Sender Reputation

ISPs use sophisticated algorithms to evaluate sender reputation. Understanding these factors helps you optimize your warmup strategy:

• Volume Patterns: Sudden spikes in volume are suspicious. Gradual, consistent increases signal legitimacy.
• Engagement Metrics: Opens, clicks, and replies indicate that recipients want your emails. Low engagement hurts reputation.
• Bounce Rates: High bounce rates (>2%) suggest poor list hygiene and damage sender reputation.
• Spam Complaints: Complaint rates above 0.1% are concerning. Even a few complaints during warmup can be problematic.
• Authentication: Proper SPF, DKIM, and DMARC configuration is essential for building trust.
• Spam Trap Hits: Sending to spam traps (abandoned or honeypot addresses) severely damages reputation.

2. The IP Warming Process

2.1 Warmup Timeline and Volume Progression

The typical IP warmup process takes 21-45 days, depending on your target volume and risk tolerance. The progression follows an exponential curve initially, then transitions to linear growth:

2.2 Different Warmup Speeds

The mySMTP Warmup Schedule Generator offers three warmup speed options:

• Conservative (45 days): Recommended for new domains, cold outreach, or when maximum deliverability is critical. Slowest ramp-up with lowest risk.
• Moderate (30 days): Balanced approach suitable for most use cases. Good combination of speed and safety.
• Aggressive (21 days): Fastest warmup for established domains with good reputations. Requires excellent list quality and high engagement.

2.3 Email Type Considerations

Different email types require different warming approaches:

Transactional Emails

• Typically have the highest engagement rates (opens, clicks)
• Can warm up faster due to expected, one-to-one nature
• Examples: receipts, password resets, shipping notifications

Marketing Emails

• Require more careful warming due to promotional nature
• Must maintain high engagement to build positive reputation
• Start with most engaged segments first

Cold Outreach

• Highest risk category—recipients haven’t explicitly opted in
• Requires longest warmup and most conservative approach
• Must maintain extremely low complaint rates (<0.05%)

3. IP Warming Best Practices

3.1 Pre-Warmup Checklist

Before beginning your warmup, ensure these critical elements are in place:

• Authentication Setup
  • SPF record properly configured and published
  • DKIM signing enabled with appropriate key length (2048-bit recommended)
  • DMARC policy published (start with p=none for monitoring)
• List Quality
  • Remove hard bounces and invalid addresses
  • Segment list by engagement level
  • Verify email addresses are legitimate and deliverable
• Content Preparation
  • Design emails that encourage engagement
  • Avoid spam trigger words and excessive promotion
  • Include clear unsubscribe mechanisms

3.2 During Warmup: Critical Metrics to Monitor

3.3 Common Mistakes to Avoid

• Skipping Days: Consistency is crucial. Never skip days in your warmup schedule, as this creates suspicious volume patterns.
• Increasing Too Quickly: Doubling volume daily or making large jumps triggers spam filters. Follow gradual progression.
• Ignoring Engagement Signals: Low opens, high complaints, or poor inbox placement require immediate attention and schedule adjustment.
• Using Entire List Immediately: Start with your most engaged subscribers and gradually expand to less-engaged segments.
• Not Monitoring Blacklists: Check major blacklists (Spamhaus, Barracuda, SORBS) daily during warmup.

4. Using the mySMTP Warmup Schedule Generator

4.1 Tool Overview

The mySMTP Warmup Schedule Generator is a tool designed to create customized IP warming schedules based on your specific needs. It uses proven mathematical models that combine exponential and linear growth patterns to optimize deliverability while minimizing risk.

The generator creates a day-by-day schedule with specific volume targets, visual progression charts, and tailored best practice recommendations for your email type and use case.

4.2 Input Parameters

The tool requires several inputs to generate an optimized schedule:

IP Address

Your dedicated SMTP server IP address. This helps track and document which IP each schedule applies to, essential for managing multiple IPs.

Email Type

Select from four categories:

• Marketing Emails: Newsletters, promotional campaigns, announcements
• Transactional Emails: Receipts, account notifications, password resets
• Mixed: Combination of marketing and transactional
• Cold Outreach: Sales prospecting, business development

Target Daily Volume

Your desired final daily email volume. The tool builds a schedule to reach this target gradually. Be realistic—start with achievable goals and scale up over time.

Warmup Speed

Choose your risk/speed preference:

• Conservative (45 days): Safest option with extended warmup period
• Moderate (30 days): Balanced approach, recommended for most users
• Aggressive (21 days): Fastest warmup, requires excellent list quality

Starting Volume

Initial daily email volume on day 1. Default is 50 emails, which is conservative and safe for most scenarios. You can adjust this based on your domain’s history and confidence level.

Domain Reputation

Indicates your domain’s sending history:

• New Domain: Never sent emails before—requires longest warmup
• Established Domain: Has sent emails but building new IP reputation
• Good Reputation History: Strong track record, can warm slightly faster

4.3 Understanding the Generated Schedule

Overview Cards

The schedule begins with quick-reference cards showing total duration, number of weeks, starting volume, and final volume. These provide at-a-glance understanding of your warmup plan.

Daily Volume Progression Chart

A visual graph showing how your daily volume increases over time. The curve demonstrates the exponential-to-linear progression pattern that ISPs recognize as legitimate sender behavior.

Detailed Schedule Table

The table provides day-by-day guidance:

• Day: Sequential day number in the warmup
• Week: Which week of warmup you’re in
• Daily Volume: Target number of emails for that day
• Increase: Number and percentage increase from previous day
• Progress: Visual progress bar showing percentage toward target

Customized Recommendations

Based on your selected email type and parameters, the tool generates specific best practices and warnings. These recommendations are tailored to your use case and should be followed closely.

CSV Export

Download your schedule as a CSV file for easy tracking in spreadsheet software, integration with sending platforms, or sharing with your team.

4.4 The Mathematics Behind the Schedule

The generator uses a hybrid growth model:

• Exponential Phase (First 70% of schedule): Volume grows exponentially, allowing for rapid yet controlled ramp-up in the early stages when volumes are still relatively low.
• Linear Phase (Final 30% of schedule): Transitions to steady linear increases as you approach target volume, ensuring stable, predictable growth that ISPs trust.

This mathematical approach mirrors natural email program growth and has been proven effective across thousands of successful warmups.

5. Advanced IP Warming Topics

5.1 Multi-IP Warming Strategies

When warming multiple IPs simultaneously:

• Stagger warmup start dates by 1-2 weeks to avoid overwhelming your list
• Segment your list across IPs by engagement level or content type
• Monitor each IP’s reputation independently
• Use the generator to create separate schedules for each IP

5.2 Re-warming After Inactivity

If you’ve stopped sending for an extended period:

• 1-2 weeks inactive: Resume at 50% of previous volume, ramp back up over 1 week
• 1-2 months inactive: Resume at 25% volume, follow 2-week ramp-up schedule
• 3+ months inactive: Treat as new IP and complete full warmup process

5.3 ISP-Specific Considerations

Major ISPs have different filtering approaches:

• Gmail/Google Workspace: Extremely engagement-focused. Low opens/clicks hurt significantly. Monitor via Google Postmaster Tools.
• Microsoft (Outlook, Hotmail): Reputation-based filtering with SNDS monitoring. Watch spam trap hits carefully.
• Yahoo/AOL: Strict volume throttling during warmup. May require slower ramp than other ISPs.
• Apple iCloud: Uses machine learning models. Consistent sending patterns and good engagement essential.

5.4 Troubleshooting Poor Warmup Results

If experiencing deliverability issues during warmup:

1. Pause immediately: Stop sending and assess the situation
2. Identify root cause: Check bounce rates, spam complaints, blacklists, authentication
3. Clean your list: Remove problematic addresses and unengaged subscribers
4. Restart conservatively: Resume at 25-50% of volume when issue was detected
5. Monitor closely: Watch metrics daily and adjust as needed

6. Conclusion

IP warming is a critical investment in your mailing’s long-term success. While it requires patience and discipline, the payoff in deliverability, sender reputation, and ROI is substantial. A properly warmed IP address is the foundation of reliable email delivery.

The mySMTP Warmup Schedule Generator removes the guesswork from this process, providing you with a scientifically-designed, customized plan based on proven best practices. By following the generated schedule and monitoring your metrics closely, you’ll establish a strong sender reputation that supports your email goals for years to come.

Remember: IP warming is not a one-time event but the beginning of an ongoing commitment to email best practices. Maintain list hygiene, monitor engagement, authenticate properly, and respect subscriber preferences. These fundamentals, combined with proper warming, will ensure your emails consistently reach the inbox.

Additional Resources

For more information and support:

• Access the Warmup Schedule Generator at mySMTP.com
• Monitor reputation with Google Postmaster Tools and Microsoft SNDS
• Check blacklist status regularly during warmup
• Contact mySMTP support for personalized guidance