No, it does not store emails offline by default (though you can configure it to use maildir and use isync to pull emails down, this is what I do in my configura

No, it does not store emails offline by default (though you can configure it to use maildir and use isync to pull emails down, this is what I do in my configuration). In my opinion this is the major design mis-step of aerc which will be corrected by a future mail client.