Mailing lists and e-mail body alteration
Problem reported by Sébastien Riccio - 10/12/2024 at 10:35 PM
Submitted
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.

Sébastien Riccio
System & Network Admin

Richard Laliberte Replied
We are currently on version 8993 due to our hosting providing doing an upgrade on our servers, and we are wondering if this is a new issue or on-going issue. we are looking to upgrade to 9049 to address some other issues we are having, but this could put a damper on the update. 

If i am reading this correctly, the issue occurs when you are sending from an external email address to a SM mailing list? or does this also happen when sending from a SM email address to the SM mailing list? We have an internal system build around the API's and sending from a SM email address, just want to know if this will break that functionality (as mentioned above) or if we are ok to upgrade as planned.

Thanks
Sébastien Riccio Replied
Hello,

It seems to me that the reason is SmarterMail is converting the charset of the body of a mail when it's not UTF-8.

In my tests where I can reproduce the issue, the original mail charset is iso-8859-1, but SM alters it and change it to utf-8, and therefore it breaks ARC checks at the recipient server because the body checksum doesn't match the original message checksum anymore.
This only happens when the mail is sent to a mailing list though. It's not affecting forwards or aliases.

I don't know if I get the issue origin correctly, but I've opened a ticket and I am waiting on SM team to be able to reproduce the issue.

I will update this thread when I get some news.

Kind regards

Sébastien Riccio System & Network Admin https://swisscenter.com

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