OT: Adding signatures to outgoing mails

[Garry]

Some time ago, I used Mailscanner slightly differently than intended, in
order to add custom signatures to outgoing mails... the place had 4
different companies, which all required a separate company signature.

On a new project, I could use this again, though I don't want to go
through the hassle of running a full MS install just to get automated
signatures added to outgoing mails ... anybody happen to know some *ix
tool or way to implement something similar?

It would also be great if I could make adding a signature depending on
the sending domain, and possibly even having some template fields that
would be filled based on a sender address ...

Tnx, -garry