Howard Miller

Grant hasn't been on this forum since he posted that question, so I doubt he'll answer.

I would start by enabling Debugging (right to Developer level) and see if the task log gives you more information.

This sounds like a cache problem, so my first thought would NOT be to connect it to the database. What has lead you to believe that this error is related to your database configuration?

It sounds like you have misconfigured your Moodle cache, somehow.

Nope.

However, we're not done yet. Where is your Moodle site hosted for a start?

I cannot overemphasise - do not try to resolve issues with connections to external sites/servers using Moodle itself. It's not what it's for - it doesn't have the diagnostic capabilities. Use a dedicated mail client or debug the protocol directly using (e.g.) telnet. It's not as bad as it sounds.

Open source (and free) mail client - Other mail clients are available.

https://www.thunderbird.net/

This ^^^

Or, if you're really keen/desperate try this https://learn.microsoft.com/en-us/exchange/mail-flow/test-smtp-telnet?view=exchserver-2019

The point is that if you have the correct parameters, you're not firewalled and the mail server is configured properly then it will work as Moodle fully supports the SMTP protocol. One of those things is wrong and it's usually easier to troubleshoot it outside of Moodle. It's very common for hosting companies and ISPs to block SMTP to a greater or lesser extent to prevent SPAM.

Yes, it's frustrating. Been there many times. I sympathise.