Exim "refused: too many connections"

Symptoms

Exim is unable to deliver emails.

Cause

A busy mail server may have an increased number of connections, and when configuration limits are reached any further connections are denied. The Exim log file /var/log/exim_mainlog will show output like the following.

CONFIG_TEXT: 2026-07-11 17:14:12 Connection from [203.0.113.0]:45774 refused: too many connections

Resolution

The Exim smtp_accept_max setting can be increased to accommodate the server's requirement.

1. Login to your WHM server as the root user.
2. Navigate to Home / Service Configuration / Exim Configuration Manager
3. Click the Advanced Editor tab
4. Search for smtp_accept_max_
5. Change the value as needed. The default is 100.
6. Scroll down and click Save

Additional Resources

How to use exigrep to search the Exim logs