smtpmail-send-it: authentication failed in response to AUTH PLAIN (emacs + mu4e + posteo)

Question

I've been trying to set of my new posteo.net email account on emacs/mu4e (I have a gmail account that works on emacs/mu4e but would like to switch). I can successfully receive emails via offlineimap but cannot send emaisl. Specifically, I get the following error message:

smtpmail-send-it: Sending failed: 535 5.7.8 Error: authentication failed: in response to AUTH PLAIN 

I have the following variables set in emacs:

  smtpmail-stream-type         'starttls
  smtpmail-default-smtp-server "posteo.net"
  smtpmail-smtp-server         "posteo.net"
  smtpmail-smtp-service        587)

I tried a few other combinations, i.e., posteo.de, smtp.posteo.net, smtp.posteo.de, as well as using ssl for smtpmail-stream-type (along with port=465), all failing with the same message. Any tips would be welcome!

Answer 1

The question was answered here: Cannot send email in emacs via smtpmail + starttls

The .authinfo file needs to include the full email address, not just the username, as login.

Answer 2

I had similar trouble, the solution being to set the following variables:

(setq smtpmail-smtp-user           "[e-mail]"
      smtpmail-default-smtp-server "posteo.de"
      smtpmail-smtp-server         "posteo.de"
      smtpmail-smtp-service        587
      smtpmail-stream-type         'starttls
      smtpmail-use-gnutls          t)

when prompted for your SMTP username and password it will look odd ([e-mail]@posteo.de) but it worked for me.

hope that helps