If your LowLoad mail service sometimes there are messages like:

amavis[26902]: (26902-20) smtp resp to NOOP (idle 422.0 s): 421 4.4.2 smtp.example.com Error: timeout exceeded

they can be ignored because the message refers to the $smtp_connection_cache filter amavis and errors in the e-mail system does not.

You can disable the caching smtp connections /etc/amavisd/amavisd.conf:

$smtp_connection_cache_enable = 0;
$smtp_connection_cache_on_demand = 0;