Sometimes you won’t be able to send/receive emails. Telnet may mention a temporary problem as follows.
telnet abc.com 25
Connected to abc.com.
Escape character is ‘^]’.
451 Temporary local problem – please try later
Connection closed by foreign host.
Upon checking the error log, I noticed the following error displayed.
2013-07-24 03:11:48 SMTP connection from [18.104.22.168]:58121 (TCP/IP connection count = 1)
2013-07-24 03:11:48 no IP address found for host abts-tn-dynamic-22.214.171.124.airtelbroadband.in (during SMTP connection from [126.96.36.199]:58121)
2013-07-24 03:11:48 H=[188.8.131.52]:58121 temporarily rejected connection in “connect” ACL: “Host is ratelimited due to multiple failure only connections (7.9/1h max:5)”
To overcome this error, I did the following. This is a cpanel server.
mv ratelimit ratelimit.bak
mv ratelimit.lockfile ratelimit.lockfile.bak
Asked the client to try again and it all worked. The ratelimit files will be generated again when exim starts processing.