quickFilter from message: Mails with own sender address are not automatically suggested for merging #52

It appears that when we define a filter through the context menu and it is from ourselves then the merge process isn't suggested: the wrong server may be used and the filter created in an invalid location.

I investigated this issue today and it's because I have emails where the message header field "accountKey" is empty. We could add a heuristic method that finds out the originating account / server through matching the from address with default identities of all accounts.