CSF blocking IPs because of Exim syntax errors

Symptoms

CSF is blocking IPs because of Exim syntax errors. The lfd.log file has messages similar to the following.

Mar  8 04:42:20 host lfd[4176295]: (eximsyntax) Exim syntax errors from 203.0.113.2 (LK/Sri Lanka/-): 10 in the last 3600 secs - *Blocked in csf* [LF_EXIMSYNTAX]

Please note that ConfigServer Security & Firewall (CSF) is third-party software and not part of cPanel's software suite. Its provision, configuration, and management are beyond the scope of our support.

Description

CSF blocks the IPs due to the values of its LF_EXIMSYNTAX and LF_EXIMSYNTAX_PERM settings.

Workaround

Edit the CSF config, set LF_EXIMSYNTAX and LF_EXIMSYNTAX_PERM values to 0, save changes, and restart CSF/LFD.

Additional resources

ConfigServer Community Forum: CSF blocking an IP because of Exim syntax errors