PTR record check -> Reject senders without PTR
Two DNS Blacklist checks configured -> Don't accept the email when detected
DNS Server: Google public DNS [18.104.22.168 / 22.214.171.124]
I face a lot of inbound SPAM, which seems to be caused to a failting DNS lookup. See two example lines from the log
Code: Select all
04/25/17 12:55:48 ME-E0114:  DNS error (9002) when resolving PTR for 126.96.36.199. Sender allowed.
04/25/17 12:55:48 ME-I0149:  5892858EF87F4BF48D280E3512DFFEB4.MAI was received successfully and delivery thread was initiated
It seems that because the reverse DNS lookup (PTR) fails, both anti-spam measurements (PTR check + DNS Blacklist check) are being skipped.
I you lookup the PTR for 188.8.131.52 on various online tools, you'll get or timeouts or 'no results found'. I expect the timeout is the issue I'm facing. But effectively this means that spam which is sent from an IP that has a faulty (or slowish) PTR DNS configuration ensures the spam being delivered on my MailEnable SMTP agent right (as further check are being skipped)?
How to counter this spam giving the above? And what is your read, a bug or edge case within MailEnable, or misconfiguration from my side?