Mailgun has thresholds in place that if exceeded will result in a domain being temporarily disabled. These limits are in place to protect your email reputation in case your system is compromised by a spammer or someone in your organization makes a large mistake.
If you do not have a good reputation tied to your domain and IP address, your email will not reach your recipients’ inboxes.
The number one reason we see people get blocked is because they have a bad mailing list. Most of these lists have bad email addresses and include spam traps. ESPs are good at recognizing bad mailing lists.
You can check your logs to see emails that are bouncing and check your suppression list for emails that we have stopped sending to as a result of bounces.
Best practices for lowering bounce rates include:
- If you think your application has been compromised, change your SMTP credentials or API key through the Mailgun control panel.
- Clean your mailing list of invalid email addresses.
- Only send emails to recipients that have signed up to receive them.
- Verify the email address is correct with a confirmation email (aka, confirmed opt-in).
- We recommend using our email verification service at the point of signup to reduce invalid email addresses.
- Don’t purchase your list or scrape websites for emails.
If your domain does get disabled, contact support after you have made the recommended changes above so we can re-enable your domain.