SMTP protocol synchronization error \(input sent without waiting for greeting\): rejected connection from .*\[<HOST>\]
SMTP protocol synchronization error \(next input sent too soon: pipelining was not advertised\): rejected .*\[<HOST>\]
rejected EHLO from \[<HOST>\]: syntactically invalid argument
rejected HELO from \[<HOST>\]: syntactically invalid argument
Connection from \[<HOST>\] refused: too many connections from that IP address
\[<HOST>\] .* host is listed in zen.spamhaus.org
\[<HOST>\] .* host is listed in bl.spamcop.net
\[<HOST>\] .* relay not permitted
\[<HOST>\] .* too many connections from that IP address
\[<HOST>\] .* rejected after DATA: This message was detected as possible malware
\[<HOST>\] .* temporarily rejected RCPT \<\S+\>: lowest numbered MX record points to local host