Exim "refused: too many connections"

Symptoms

Exim is unable to deliver emails.

Description 

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.

2023-01-26 17:14:12 Connection from [192.168.20.1]:45774 refused: too many connections

Workaround

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

1. Go to "Home / Service Configuration / Exim Configuration Manager"
2. Click the Advanced Editor tab
3. Search for smtp_accept_max
4. Change the value as needed. Example: 200
5. Scroll down and click save