Sendmail problems with Raspbian Buster

"5.7.0 Authentication required" error in Thunderbird on my Macbook when trying to use Sendmail on my Pi for outgoing mail.  Also Alpine in a ssh shell would not send.

By comparing the setup with my exist PI, I eventually discovered that libsasl2-modules was not installed.

Nikon photo contest international email problem

The process to send your photos to this contest starts with filling in a web form with your email address and a password. They then send you an email with a website URL.

Unfortunately, although I can see from my mail server log that they attempted to email me, their email was rejected by my mail server because they sent from a non-existent domain:

Sep 1 20:38:16 malander sm-mta[22038]: m81JcGjv022038: ruleset=check_mail, arg1=, relay=mailx.photohighway.co.jp [211.13.226.3], reject=553 5.1.8
... Domain of sender address sys.npci@2008-09.nikon-npci.com does not exist
Sep 1 20:38:17 malander sm-mta[22038]: m81JcGjv022038: from=, size=0, class=0, nrcpts=0, proto=SMTP, daemon=MTA-v6, relay=mailx.photohighway.co.j
p [211.13.226.3]


Maybe this is happening all over the world at this very moment and, if you don't have access to the mailserver logs, you wouldn't know why you didn't receive the email from Nikon.

After browsing my list of logins, I discovered that I already had been through this process about three years ago so they already have a (different) email address and password for me. But I am a bit reluctant to use it as they might try to email me again!