Hello,
Some customers reported that the mails sent to their SmarterMail mailinglists often ends in Spam/Junk folder of the mailing list subscribers (on different external mail services).
I did some tests and I was able to confirm this as well as maybe found the problem origin.
When a mail is sent to a SmarterMail mailinglist, the body of the mail seems altered and therefore it fails DKIM/ARC checks.
To reproduce this:
- I created a mailing list with a subscriber that points to my gmail account.
- I created an alias that points to my gmail account.
- I created a mailbox that forwards to my gmail account
Then, Isent a mail from my outlook.com account to these 3 addresses I've created to check the results.
- The mail sent to the mailing list triggers a body mismatch at gmail and goes directly in junk mail:
- The mail sent to the alias pass all checks at gmail, and doesn't end in junk mail:
- The mail sent to the mailbox with a forward pass all checks at gmail, and doesn't end in junk mail:
As you can see on the screenshots, the mails sent via the alias and forwarded mailbox matches the original message body which is (extracted from our incoming gateway):
However, the one sent to the mailing list has it's body altered because the content-type is altered by SM from iso-8859-1 to UTF-8 for an uknown (to me) reason and breaks the ARC body hash.
This seems to happen only when SM mailing list engine is used.
A fix for this would be very welcome.
Thanks a lot.