Variable: smtpmail-servers-requiring-authorization
smtpmail-servers-requiring-authorization is a customizable variable
defined in smtpmail.el.gz.
Value
nil
Documentation
Regexp matching servers that require authorization.
Normally smtpmail will try first to send emails via SMTP without user/password credentials, and then retry using credentials if the server says that it requires it. If the server name matches this regexp, smtpmail will send over the credentials on the first attempt.
This variable was added, or its default value changed, in Emacs 27.1.
Probably introduced at or before Emacs version 27.1.
Source Code
;; Defined in /usr/src/emacs/lisp/mail/smtpmail.el.gz
(defcustom smtpmail-servers-requiring-authorization nil
"Regexp matching servers that require authorization.
Normally smtpmail will try first to send emails via SMTP without
user/password credentials, and then retry using credentials if
the server says that it requires it. If the server name matches
this regexp, smtpmail will send over the credentials on the first
attempt."
:type '(choice regexp (const :tag "None" nil))
:version "27.1")