Hello, > <=SEND=> > AUTH PLAIN long-base64-encoded-string-here== > > <AUTH-PLAIN> > 535 Incorrect authentication data There are some variations of SMTP AUTH PLAIN. One possibility is mew-smtp-auth-plain-authorize-id. This defaults to nil. What will happen if set it to t? (setq mew-smtp-auth-plain-authorize-id t) --Kazu