Keyword based custom subject warning

[Damian]

> apparently, our users are receiving emails containing links and /or 
> references to various publications, some of which are considered 
> 'predatory'. Emails usually contain ISSN (International Standard 
> Serial Number) and the idea is to scan the body of an email for the 
> ISSN and if it matches one on the 'blacklist', the subject of the 
> email should be prepended with some specific warning (other than 
> ***SPAM***).
>
> We're already using Amavisd-new on our inbound SMTP server, so I 
> wonder if that would be possible with it?

This would have been a use-case for [1]. The corresponding Amavis 
feature is still unreleased, unfortunately.

[1] 
https://spamassassin.apache.org/full/3.4.x/doc/Mail_SpamAssassin_Conf.html#subjprefix