⚠️ Common SMTP Connection Issues

Here are the most frequent connection problems and what they typically mean:

1. Connection Timed Out

Error Example:
Connection timed out or Could not connect to SMTP host

Cause:
The client could not reach the SMTP server. This is often due to:

• Network issues
• Firewall rules blocking port 25 or 587
• SMTP server being down or unreachable

Fix:

• Check your internet/network connection.
• Ensure the SMTP server address is correct.
• Confirm that the relevant SMTP ports are open.
• Try telnet to test connectivity:
  telnet smtp.example.com 587

2. Authentication Failed

Error Example:
535 Authentication failed or SMTP Error: Could not authenticate

Cause:
The server rejected the login credentials.

Fix:

• Double-check the username and password.
• Make sure the SMTP server requires authentication (some internal relays do not).
• Ensure the account is active and not locked.

3. TLS/SSL Errors

Error Example:
SSL: CERTIFICATE_VERIFY_FAILED or Handshake failed

Cause:
Issues with establishing a secure connection:

• Outdated SSL/TLS protocols
• Invalid or expired server certificates
• Client doesn't trust the server certificate authority

Fix:

• Make sure your client supports modern TLS versions (TLS 1.2+).
• Verify the SMTP server’s certificate.
• Update system CA trust store or disable certificate validation (for testing only).

4. Blocked by Firewall or ISP

Error Example:
No specific error, but connection silently fails or times out.

Cause:
Many ISPs block outbound traffic on port 25 to reduce spam.

Fix:

• Try using ports 587  (with STARTTLS).
• Contact your ISP to unblock port 25.
• Use a relay service like mySMTP that supports alternate ports.

5. Too Many Connections / Throttling

Error Example:
421 Too many concurrent SMTP connections or 421 Service not available

Cause:
The server is limiting how many connections a single client can make.

Fix:

• Implement connection pooling or reuse connections.
• Reduce sending rate.
• Work with your ESP to increase connection limits if needed.

6. DNS Issues

Error Example:
Temporary failure in name resolution

Cause:
SMTP server hostname can't be resolved.

Fix:

• Check that the hostname is correct.
• Ensure your server has working DNS settings.
• Try using the SMTP server’s IP address as a test.

🛠️ General Troubleshooting Steps

1. Ping or traceroute the SMTP server.
2. Use telnet or openssl to manually test the connection.
3. Check logs from your email client or sending application.
4. Verify server status from your email service provider.
5. Temporarily disable antivirus/firewall to rule them out.
6. Try from another network to isolate the problem.

✅ Tips for Reliable SMTP Connections

• Use modern encryption (TLS 1.2+).
• Don’t hardcode IPs—use hostnames that can be updated.
• Monitor connection rates and timeouts.
• Use connection retries with backoff strategies.
• Keep your client libraries updated.

Title: Why Are My Emails Going to Spam?

If your emails are landing in spam instead of the inbox, there could be several contributing factors. Understanding these causes can help you improve your email deliverability and ensure that your messages reach the intended recipients.

Common Reasons Emails Go to Spam:

1. Poor Sender Reputation
   • Your domain or IP address may have a low sender score due to previous spam complaints or poor engagement.
   • Check your sender reputation using tools like Google Postmaster Tools or third-party services.
2. Lack of Authentication (SPF, DKIM, DMARC)
   • Email providers check authentication records to verify legitimacy.
   • Ensure your domain has properly configured SPF, DKIM, and DMARC records.
3. High Spam Complaint Rate
   • If recipients frequently mark your emails as spam, email providers will flag your future emails.
   • Use clear unsubscribe options and avoid sending unsolicited emails.
4. Poor List Quality
   • Sending emails to invalid or inactive addresses can increase bounce rates and harm deliverability.
   • Regularly clean your email list and use double opt-in methods.
5. Spam Trigger Words and Content Issues
   • Certain words commonly associated with spam can trigger filters (e.g., "free," "winner," "guaranteed," "limited-time offer," "urgent," "make money fast").
   • Avoid excessive punctuation, all caps, or misleading subject lines.
   • Maintain a balance of text and images, as emails with too many images or links may be flagged.
   • Test emails with spam check tools before sending them.
6. Sending Too Many Emails at Once
   • Large email blasts from a new or low-reputation domain can be flagged as suspicious.
   • Warm up your email sending and use proper email throttling techniques.
7. Blacklisted IP or Domain
   • Your sending IP or domain may be blacklisted due to prior spam activity.
   • Check blacklists like Spamhaus or MXToolBox and request removal if necessary.
8. Misconfigured Email Headers
   • Incomplete or improperly formatted email headers can cause messages to be marked as spam.
   • Ensure your email software or service provider adheres to proper email header standards.
9. Lack of Engagement
   • Low open rates and low click-through rates signal to providers that your emails are not wanted.
   • Personalize subject lines, segment your audience, and encourage interaction.
10. Shared IP Reputation Issues

• If using a shared email service, other users’ behavior can impact your reputation.
• Consider using a dedicated IP for better control over email deliverability.

11. Poorly Optimized Email Design

• Emails that are not mobile-friendly or have broken HTML code may be flagged as spam.
• Use responsive design templates and preview your emails across devices.
• Avoid embedding large files, using too many fonts, or adding excessive colors and styles.

12. Lack of Proper Unsubscribe Options

• Failing to provide a clear, working unsubscribe link can increase spam complaints.
• Ensure users can easily opt out of emails, and process opt-outs promptly.

13. Excessive Use of Attachments

• Sending large or unexpected attachments can trigger spam filters.
• Use cloud links for file sharing instead of attachments when possible.

How to Improve Email Deliverability:

• Authenticate your domain with SPF, DKIM, and DMARC records.
• Regularly clean your email list to remove inactive or invalid addresses.
• Use double opt-in to ensure recipients genuinely want your emails.
• Monitor your sender reputation and blacklist status.
• Write engaging, non-spammy content that follows best practices.
• Test your emails using spam check tools before sending them.
• Encourage engagement by personalizing subject lines and content.
• Optimize your email design for readability and responsiveness.
• Provide clear unsubscribe options to reduce complaints.

By addressing these factors, you can reduce the likelihood of your emails being marked as spam and improve your overall email deliverability.

Checking Email Logs and Headers for Debugging

When troubleshooting email delivery issues in mySMTP, checking email logs and analyzing email headers can help diagnose issues such as delays, rejections, or failures. This guide covers how to access email logs and interpret headers for debugging purposes.

1. Accessing Email Logs in mySMTP

mySMTP provides log access for tracking sent, received, and failed emails. To check logs:

1. Login to the mySMTP Dedicated Server Dashboard:
   • Navigate to the login page (https://dashboard.mysmtp.com).
   • Enter your credentials to access the user dashboard.
2. Login to the mySMTP Shared Account Dashboard:
   • Navigate to the login page on (https://mysmtp.com).
   • Enter your credentials to access the user dashboard.
3. Go to the Logs Section:
   • Locate the "Search Logs" or "Statistics" section.
   • Use filters (e.g., sender, recipient, date range) to refine the log search.
4. View Log Details:
   • Click on a specific email entry to see details such as status codes, timestamps, and delivery attempts.
5. Export Logs (if needed):
   • Some mySMTP versions allow exporting logs in CSV format for further analysis.

2. Understanding Email Logs for Debugging

Email logs contain useful data points to diagnose email issues:

3. Analyzing Email Headers for Troubleshooting

Email headers provide additional insights into email routing, authentication, and delays.

1. Find the Email Header:
   • In the recipient's email client, open the email.
   • Look for "View Source" or "Show Original" to access headers.
2. Key Header Fields to Analyze:

3. Common Issues and Fixes:
   • Delayed Emails: Check the "Received" timestamps to identify slow servers.
   • Email Rejected (550 errors): Ensure the sending IP isn’t blacklisted and SPF/DKIM/DMARC are correctly set.
   • Spam Flagged Emails: Adjust email content to avoid trigger words and ensure proper authentication.

4. Using mySMTP Support for Further Assistance

If logs and headers do not resolve the issue, consider:

• Checking mySMTP’s status page for service disruptions.
• Contacting mySMTP support with relevant log entries and headers.
• Reviewing sender reputation and spam scores to ensure email deliverability.

By leveraging email logs and headers, users can efficiently diagnose and resolve email delivery issues within mySMTP.