User:Mkmelin
From MozillaWiki
No, my understanding of the mail.identity.default.autocompleteToMyDomain option is that it appends the correct domain *as you are typing in a new contact.*
If you have a list with local domain email addresses, but they are unqualified
for example
joe_smith
instead of
joe_smith@domain.com
you will still get an error when you try to send this as part of a list even if the autocomplete option is set to true.