On Sat, 21 Jan 2012 16:35:10 +0100, Simon Campese <notmuchmail_org@campese.de> wrote:
> Dear Community,
> 
> I've got my own domain and when registering or shopping at some website,
> I always use email addresses of the form "websitename@mydomain.org", so
> for example I use "amazon@mydomain.org" when shopping at amazon. The
> reason for this is categorizing incoming mail on the one hand, and
> immediately being able to spot the source of spam on the other hand. 
> 
> I would like to implement the following behaviour: When replying to a
> mail that has "something@mydomain.org" in the "To"-header, I would like
> to have the "From"-header of the reply to be automatically set to this
> address. 
> 
> Is there some kind of reply-hook in notmuch where one could put an
> appropriate function? 

Do you have all those email addresses in the user.other_email
configuration option in your ~/.notmuch-config? It should do the trick,
though I can see that it might get a bit tedious if you use plenty of
email addresses like above.

BR,
Jani.