Received emails from Amazon SMTP servers go to Spam due to lack of RDNS

1

Hello all,

Is it just me, or has anyone noticed that received emails sent via Amazon Simple Email Services (SES) SMTP servers (xxxx.amazonses.com) are intermittently sent to Spam because the RDNS lookup fails? I’ve noticed this over the past month, and only emails received via Amazon SMTP servers are affected (i.e. it is not a global RDNS lookup issue on my mailinabox). The RDNS lookups do intermittently succeed, so some emails make it through, but others no.

To clarify, I am not using AWS to host my mailinabox. This applies to emails received on my box from others who happen to use Amazon’s SMTP servers (including Amazon itself for online shopping).

This only started happening ~1 month ago. I haven’t made any changes to my mailinabox configuration during that time, though there have been the regular updates to the installed Linux packages (via sudo apt upgrade). So it seems there may be something intermittently wrong with Amazon’s DNS?

Thanks!

2

I have not noticed this. To be sure: how did you determine that is the reason those mails go to spam? (hint: in the headers of received mails are usually multiple reasons for spam scoring. Those reasons together have a total score which will move mail to spam if above a threshold)

3

Several of the reasons in the headers point to an RDNS issue. For example (all in the same header):

  • 1.3 RDNS_NONE Delivered to internal network by a host with no rDNS
    * 2.0 HTML_FONT_TINY_NORDNS Font too small to read, no rDNS
    * 1.7 FONT_INVIS_NORDNS Invisible text + no rDNS
    * 2.5 NORDNS_LOW_CONTRAST No rDNS + hidden text

Taken together, the above RDNS-related reasons push the spam score past the threshold.