Outgoing Emails being flagged as Spam due to Reverse DNS Lookup Failed

Problem reported by Chase Casebonne - 1/21/2019 at 2:45 PM

Resolved

Since we have implemented Smartermail Version 17 6948 we are finding that outgoing emails will fail a Reverse DNS Lookup and thus gain a Spam Weight greater than 30 causing the email not to go out. It will only happen to specific email addresses. I am able to send to some email addresses on a domain but not all. We also host multiple domains that are experiencing the issue. Thing is that one of the domains it is happening on has a Reverse DNS that is correct. Has anyone experienced this? For now I have increased my threshold of outgoing Spam weight to allow this email to go out.

5 Replies

Reply to Thread

echoDreamz Replied

1/21/2019 at 3:00 PM

Have you checked if RDNS checks are enabled for outgoing SMTP? It should never be enabled for outgoing, IMO, SM should "N/A" outgoing checks for RDNS.

Matt Petty Replied

1/21/2019 at 4:38 PM

Employee Post Marked As Resolution

Chris you are onto something, I have a feeling RDNS outgoing should not be allowed. I'm not sure if we intended this to be enabled for outgoing, in fact I'm having a hard time wrapping my mind around how it's functioning, I guess it isn't. It was made for verify the senders addresses with their IPs, not sure why SM would check this for outgoing since it is the sending server.

For now disable outgoing, I'm going to investigate if we need to remove it.

EDIT: I think SPF is in the same boat, should maybe be disabled for outgoing. I'm going to look more into this tomorrow. These are both checks to verify identities and should not be needed for outgoing spam.

Matt Petty Senior Software Developer SmarterTools Inc. www.smartertools.com

echoDreamz Replied

1/21/2019 at 5:03 PM

There is no reason to check outgoing (authenticated) messages against SMTP level checks IMO. Especially RDNS and SPF. Even checking against blacklists like Barracuda etc. is not a great idea. Content checks like Sniffer, Cyren etc. fine, but checking a client IP (especially residential ips) is bound to cause major headaches.