I upgraded to Thunderbird 3.0 shortly after it was released, and I'm
pleased with many of the new features in it. However, one issue I'm
encountering now that I didn't see in version 2 is an issue with the
contact auto completion feature. I have several contacts who have
multiple email addresses, and I send emails to the different addresses
depending on the topic.

In the contact entry for them, the "email" field has the address that
I would like to be the default. In the "additional email" field I have
the secondary address. However, when I go to compose an email and type
the first few characters of the contact's name, the list of email
addresses that display are ordered alphabetically. I would much prefer
that the primary email be at the top of the list. I haven't seen a
setting to fix this anywhere. Is there a fix for this, or is this
something that should be reported to the developers?