Mail fails to deliver due to corrupt /etc/domain_secondary_mx_ips.cdb file

Symptoms

Corruption in the /etc/domain_secondary_mx_ips.cdb file can cause Exim to fail to deliver messages with an error like this:

temporarily rejected RCPT <cptest@domain.com>: cdb: corrupt
cdb file /etc/domain_secondary_mx_ips.cdb (too short)

Description

This issue occurs when corrupted data is written to the file--for example, an IP address with an extra digit at the end:

[root@server]# /scripts/dumpcdb /etc/domain_secondary_mx_ips.cdb 
$VAR1 = {
          'domain.com' => '192.0.2.502'
        };

Workaround

Run this command to recreate the /etc/domain_secondary_mx_ips.cdb file cleanly:

/usr/local/cpanel/bin/servers_queue queue build_secondary_mx_cache