High spam score

I managed to resolve the -1.596 FORGED_MUA_MOZILLA issue by removing the user agent from the email header when sending from Thunderbird.

Hello,

Have you tried to send a generic test email via SES? Does it works fine?

What is the content that you are trying to send via SES?

Checking few blogs online I could find the below information; can you try fixing/removing those and try again?

FORGED_MUA_MOZILLA ---> Forged mail pretending to be from Mozilla
T_BTC_ORG ---> Bitcoin wallet ID + unusual header

Regards,
Gaurav @ AWS

Thanks for taking a look Gaurav.

I narrowed the FORGED_MUA_MOZILLA issue down to Thunderbird. If I send through SES mail servers using Thunderbird then my emails get marked down for FORGED_MUA_MOZILLA.

Using Thunderbird with other mail servers doesn't result in this issue. To resolve this I have simply removed the user agent in the Thunderbird config settings.

It took me a while to figure out where T_BTC_ORG was coming from, but I eventually realised at the bottom of the email I was testing there was a spam email included. I had been reassuring my client the spam email was nothing to worry about but it was deep down in our email thread so I missed it. I was testing that email thread in particular because I noticed that my reply to my client had gone in the spam folder.

After resolving the user agent issue and testing a clean email I am getting a perfect 10/10 in the mail tester.

I am glad that you were able to resolve this.

Regards,
Gaurav @ AWS

Hello, I'm seeing this as well and the solution of removing the thunderbird header worked, however, I'm wondering how we escalate this up to Amazon support... I'd think it's an issue that possibly they can resolve? Since I"m sending FROM thunderbird I'm clearly not pretending to be using thunderbird... If it only happens with SES and not other smtp providers maybe it's something they can fix...??

In case anyone's still encountering this, I found that the FORGED_MUA_MOZILLA score is now a more serious spamassassin penalty (2.309) and fixing it is not as simple as it appears. The solution above doesn't say how to remove the header in Thunderbird, and the only solutions I could find when Googling were out of date and wrong.

In Thunderbird 102.1.2 the "Advanded Settings" option has moved to Settings > General > Config Editor. The value you need to change (probably) doesn't exist yet, you have to add it as a new value called general.useragent.override. I suggest setting it to something like "Thunderbird" (select "String" and the plus symbol). Leaving it blank will cause problems with DKIM signing so don't do that.

If you change your mind, there is a rubbish bin symbol you can click to remove it and restore the default behaviour (this wasn't possible in older versions of Thunderbird).

This seems to solve the problem for me - spam scores are now normal on messages I send from Thunderbird.