Emails sent with Epyrus are scoring low according to SpamAssassin Topic is solved

[athenian200]

Outlook uses User-Agent.

Where did this information come from? Mozilla seems to mistakenly think this as well, but I've tested.

I checked some e-mails sent with recent versions of Outlook, and there is no User-Agent header. Outlook in the past did apparently send User-Agent for NNTP (back when it had support for that), but not for e-mail. Mozilla may have also been confused because older versions of Thunderbird would display X-Mailer from other clients as User-Agent in the header of e-mails by default, when you don't click on view source. So if you got that info from them, I think that's where the misinformation originated.

There is a draft that suggested it for mail and it is BCP.
https://datatracker.ietf.org/doc/html/d ... r-agent-00

Interesting, this draft would actually have made both headers acceptable, because they are the most common. But it seems to have been expired/rejected for some reason? However, one piece of data in it is worth noting... your own draft shows that the people trying to write a standard noted that Outlook uses X-Mailer, not User-Agent.

In my opinion, spam filters must not check mails for "valid" or "common" User-Agent or X-Mailer headers, as they are not required.

Yeah, but if I can lower my SpamAssassin score by changing how my mail client identifies itself because it looks so close to a valid Mozilla string that they think I am "forging" it, then I don't mind changing it. I just don't understand the logic of that rule, all it does is require malicious actors to do a better job forging a Mozilla UA.

[Pentium4User]

Outlook uses User-Agent.

Where did this information come from? Mozilla seems to mistakenly think this as well, but I've tested.

From mails that came in to my inbox.
They are originating from Outlook for Mac.

Code: Select all

User-Agent: Microsoft-MacOutlook/16.79.23111718

Windows Outlook doesn't seem to send User-Agent.

Outlook in the past did apparently send User-Agent for NNTP (back when it had support for that), but not for e-mail.

Outlook as part of MS Office or Outlook Express (later named Windows Mail and Windows Live Mail)?
Did Outlook (part of MS Office) really support NNTP?

There is a draft that suggested it for mail and it is BCP.
https://datatracker.ietf.org/doc/html/d ... r-agent-00

Interesting, this draft would actually have made both headers acceptable, because they are the most common. But it seems to have been expired/rejected for some reason? However, one piece of data in it is worth noting... your own draft shows that the people trying to write a standard noted that Outlook uses X-Mailer, not User-Agent.

As long as it is a draft, it is non-standard to use User-Agent in email.

In my opinion, spam filters must not check mails for "valid" or "common" User-Agent or X-Mailer headers, as they are not required.

Yeah, but if I can lower my SpamAssassin score by changing how my mail client identifies itself because it looks so close to a valid Mozilla string that they think I am "forging" it, then I don't mind changing it. I just don't understand the logic of that rule, all it does is require malicious actors to do a better job forging a Mozilla UA.

Completely true. Even whitelisting certain UA is a bad behaviour as many UAs exist, not only from MUAs, also from software that generates mail.

[athenian200]

Outlook as part of MS Office or Outlook Express (later named Windows Mail and Windows Live Mail)?
Did Outlook (part of MS Office) really support NNTP?

I did actually use Outlook Express back in the early 2000s, now that I think about it. I couldn't afford Outlook back then, so I didn't have it. Apparently people did often use third-party extensions to support newsgroups on Outlook, but that's not official support, and there was a way to put Outlook Express into a news-only mode so that you could use Outlook for mail and Outlook Express for newsgroups. I was also thinking of how Outlook doesn't seem to support RSS feeds directly now, but I have a folder in my account from back when it did, so I assumed something similar must have happened with newsgroup support.