Our GWIA is servicing two internet domain names (xx@domain1.de and xx@domain2.de)

incoming mail works fine, the GWIA handles both domainnames

At this time, we have a preferred domain (domain1.de) for outgoing mails.
Is it possible to change this not as a global setting but just by request of a single user ??

So if the user writes an email, before clicking on "Send" he should be able to choose the outgoing address (either user@domain1.de or user@domain2.de) or anything like this...