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  • From: Ruud Baart <address@concealed>
  • To: address@concealed
  • Subject: [sympa-users] Message-Id
  • Date: Tue, 21 Dec 2021 22:11:00 +0100


in the postfix/amavis/spamassasin log the spam score of an email from a sympa list is like this:

X-Spam-Status: No, score=0.313 required=6.31 tests=[AWL=0.643, BAYES_00=-1.9,

The FORGED_MUA_MOZILLA score is quite high. It is not 100% clear for me why but I guess it has to do with the SMTP header Message-ID field combined with the User-Agent field. In this case it is something like this:

Message-Id: <adherents-loisir-pour-tous-st-andre-le-desert.77@anonymous>

And the message was sent with Mozilla Thunderbird

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101

The forced sender, as defined in this list, is, as can be seen in the Sender field:

	Sender: address@concealed

If I understand the spamassassin rule correctly the message-id field is not conform Mozilla and therefor suspected. I suppose the message-id is this way because in the list definition is defined to overwrite the from field and it has to be unique for every message.

I have read some information about this field. I assume the generated message-id is correct and unique. But perhaps the message id is not conform the recommendations as described in

I propose two solutions:

1) Is it not better to generate the message id in something like


where id is some unique ID as described in I quote: In summary, one possible approach to generating a Message-ID would be:

  • Append "<".
  • Get the current (wall-clock) time in the highest resolution to which you have access (most systems can give it to you in milliseconds, but seconds will do);
  • Generate 64 bits of randomness from a good, well-seeded random number generator;
  • Convert these two numbers to base 36 (0-9 and A-Z) and append the first number, a ".", the second number, and an "@". This makes the left hand side of the message ID be only about 21 characters long.
  • Append the FQDN of the local host, or the host name in the user's return address.
  • Append ">".

This approach would give a better message-id but perhaps still not conform the spamassassin rules because of the value of the User-Agent field.

2) An option to change the User-Agent field in a standard like User-Agent: Sympa/6.2.66 or just remove the User-Agent field.

What do you think?

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