On Thu, Mar 19, 2020 at 03:06:38PM -0400, Howard Trachtman wrote:
> i searchd the archives for authentication failed and didnt' see this issue.
> 
> I used to work with rms at MIT. really stuck with this problem, mit tech
> support couldn't figure it out
> 
> I am using GNU Emacs 25.2.2 (x86_64-pc-linux-gnu, GTK+ Version 3.22.21) of
> 2017-09-22, modified by Debian
> on athena at MIT.
> 
> I was locked out of my account and my password was reset on Monday.
> 
> Now, I can no longer send emails from emacs, I get this error:
> Sending failed: 535 5.7.0 authentication failed in response to
> aGR0MjAxMkRERA==

Judging by what I see, your Emacs mail client is failing to
authenticate to the SMTP server to get out the mails.

The 535 looks very much like an SMTP error code coming back
from the server.

Double-check your mail credentials with your system administrator.
As to how you put that in your Emacs configuration -- that'll
depend which mail library you are using. If you tell us, someone
might have more hints.  

That's something I'm definitely out of my depth.

Cheers
-- tomás