Mail Filtering

In this article, we will explain about mail filtering and mail sending limits.

One of the most widespread types of abuse is spam. We take abuse seriously and have implemented safeguards to handle the issue effectively. To keep systems healthy, Heficed limits the number of email messages that can be sent from IPs and domains via Port 25.

Currently, the limits are as follows:

  • The base limit is 4500 emails/hour
  • Should the algorithm detect any patterns that are indicative of spam or abuse emails, the limit is automatically reduced to 3000/hour
  • Emails with a high spam score are limited to 50/8 hours
  • Emails with infected attachments are bounced immediately

Once you reach either of these limits, you can only send new emails as soon as the time set by the limit has elapsed since the first email was sent. This prevents traffic from spiking and equalizes the load.

You will receive a message if you reach the limit. The message will inform how your emails were classified.

NOTE: If we observe the same IP hitting the spam limit repeatedly, the range will be blocklisted to retain its reputation.

To improve the quality of your messages and mailing practices, we suggest referring to Sender Best Common Practices presented by M3AAWG.

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If you have any questions about mail filtering, do not hesitate to contact support at or your assigned account manager.

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