Comment 96 for bug 357864

I think this enhancement is still a lot needed. You can't require a user to add an identity each time he uses a new email box.

some email provider allow to aliases their account to multiple variants like gmail (account <email address hidden> could received email to <email address hidden>) or otherinbox (account @aaa.otherinbox.com could received all email to <email address hidden>). You could create one at anytime.

Thunderbird needs to allow for this kind of account to edit "on-demand" the From field and maybe create automatically an identity for them (with a description to remember creation date). It could be the same when receiving an email on a know alias pattern (TB could suggest adding this identity)

I agree it seems not adequate for standard user but "advanced" one could enabled it.