General help

I'll also add that I have tried sendmail, postfix, ssmtp, and msmtp from various google tutorials. I haven't gotten any of them work. Maybe I'm screwing up some of the settings. No idea. I can follow tutorials but not debug errors.

I also have several domains with Bluehost. I've tried setting up an email on bluehost from one of my domains and using the recommended settings for the SMTP server in Moodle. Also didn't work. Again, maybe I'm missing a setting somewhere, but I don't know where to check for error codes or how to debug it.

I need some dead simple settings for sending email from this server or another non-GMail SMTP server. Thanks.

So your school (or your schools network) does not have an 'official' SMTP server that you can access?

The chances are that outgoing SMTP will be firewalled to prevent spam from inside the network. This is pretty standard these days.

Am curious as to why Google's SMTP was acceptable at one time and now not (not so obvious to some ... like me).

Does your entity have an SMTP server used for the internal/private network?

Sending directly from the moodle server itself can be done with postfix or sendmail, but you will have to get cooperation of network folks and DNS server admnistrator.   When you setup either postfix or sendmail did you attempt to send any message from the server itself (not via Moodle) with something like pine or alpine (text based mailer)?    Did you check the mail servers logs to see why messages bounced back or couldn't be delivered?

As Howard has said, port 25 is might be blocked at the boundary firewall so no matter what you try to setup on the Moodle server, mail will never leave your private network on port 25.

The successful sending of mail is dependent up not only network but also DNS.    For the Moodle server to be able to send mail successfully, DNS for your TLD where the moodle FQDN already has a record would need other mail related records in DNS ... spam checkers now check for MX, SPF, DKIM, blackhole list like SpamHause, + others and even reverse DNS of the server from which mail comes to determine if the message qualifies as or amasses enough 'points/characteristics' to be tagged as SPAM.

From your linux server try this from the command line:

dig yourtopleveldomain -t TXT

where yourtopleveldomain is something like myschool.net

Out put of that DNS query you might additional records for SPF or other.   Recognize any of them?

Do the same for the FQDN of your Moodle server:

dig moodle.yourtopleveldomain -t TXT

Here's an example of a server that runs sandbox Moodles ... it's IP address among those IP blocks listed in the return of the DNS query:

dig tcea.org -t TXT

You will see google and sendgrid as well.

No real simple answer to such a simple question, am afraid.

'spirit of sharing', Ken