mailchannels.net spam filtering service identifies email I send with Android Thunderbird 8.2 as spam.

[thechrisbaker]

Checklist

• I have used the search function to see if someone else has already submitted the same bug report.
• I will describe the problem with as much detail as possible.

App

Thunderbird for Android

App version

8.2

Where did you get the app from?

Google Play

Android version

15

Device model

Pixel 7A

Steps to reproduce

My host is Hostinger.io. When I send emails (IMAP--haven't tried POP) or reply to emails going to several different addresses, including @ gmail.com, att.net, and others, the service (running on the recipient's server) mailchannels.net identifies my messages as spam and bounces them back. I have to click a link that says 'this message is not spam,' and after some time, I can resend the same message. I contacted mailchannels support to find out how to fix this so it wouldn't keep happening. (see their reply below)

Expected behavior

Their service does not like the way Android Thunderbird formats is headers. My emails are not flagged if I use K9 or my host's web interface.

Actual behavior

Here's what mailchannels.net said about my messages appearing to be spam:
"While checking the logs for the account [email protected] I could see that the emails from the account were blocked with the error "5.7.1 [CS] Message blocked." This happens when the mail content contains spam patterns. Here, the reported CS error is associated with the email's message ID being seen as "forged" or improperly formatted when sent from the Thunderbird client. Here, the Thunderbird Android App may not be generating a proper or recognisable message ID that aligns with MailChannels' filtering criteria."
I can include headers from both K9 (successfully sent) and Thunderbird (bounced) messages so the cognoscente (you kind folks) can compare and evaluate.

Logs

(logging does not seem appropriate for this issue--am I wrong about that?)

[NathanHbt]

Same issue here with Thunderbird for both computer and mobile.
The problem seems to stem from the "message-id" which appears to be malformed according to current standards. Mailchannels is blocking the emails due to this malformed "message-id".

[FrancisGrignon]

I contacted mailchannels and they mentioned the same thing:

The reported CS error is associated with the email's message ID being seen as "forged" or improperly formatted when sent from the Thunderbird client. Here, the Thunderbird Android App may not be generating a proper or recognizable message ID that aligns with MailChannels' filtering criteria.

In this case, please ensure that you're using the latest version of the Thunderbird application. Sometimes, issues like this can be resolved by simply updating the email client/MUA, as newer versions may handle headers more correctly and align with the standards expected by spam filters. Also, double-check the SMTP settings in Thunderbird to ensure that the outgoing mail server is properly configured. Incorrect settings might cause malformed headers or other issues.

[cketti]

The Message-ID header is simply a UUID followed by the domain part of the user's email address, e.g. Message-ID: <[email protected]>.

This is perfectly valid and works with every other email provider. We have no plans to change this to accommodate the broken spam filter of one provider.

[kewisch]

@FrancisGrignon If you want to deal with mailchannels support you could try to find out what "standards" they are referring to. I can't find anything in the relevant RFCs that would indicate a UUID is not permitted. I'm going to close this issue for now, but if they can point to a reasonable standard then we might reconsider.

[NathanHbt]

Mailchannels informed me today that they have implemented a workaround to prevent emails from Thunderbird Mobile from being blocked. We'll see how well it works in practice.

[thechrisbaker]

NathanHbt, thank you.
Based on previous response, I've migrated back to K9 for now. Please let us know how their update performs.

[cketti]

Probably caused by #8853