Hi, In smtpmail.el, protocol messages are getting downcased with respect to current locale. For instance, it downcases AUTH methods (LOGIN, PLAIN, etc.) and then compares them with the related downcased symbols '(login plain ...). And in Turkish, a downcased I is ı (dotless i), not i. Therefore, comparison fails because of logın != login or plaın != plain. IMHO, downcased must be applied using en_US locale.
To reproduce the problem, start emacs with LC_CTYPE=tr_TR prefix and try to send a mail via smtpmail package. Regards.
