Mailing lists and e-mail body alteration

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

https://swisscenter.com

Richard Laliberte Replied

10/15/2024 at 11:20 AM

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

10/15/2024 at 11:34 AM

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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