The question is. There is Thunderbird and there is a customer with two emails. He writes always with these e-mails. Sometimes with one, sometimes with another. Is there a solution to that, if you reply, the letter was always formed on the two e-mail immediately. Machine. For example stretched with address book all of his soap, or something else... Whatever...
Like a trivial task, and how to do it solution can't find... Extension would have saved probably, but it seems that there are not looking.