just to be clear.

Incoming mail comes through one of two protocols. POP or IMAP. Outgoing mail goes using SMTP regardless of the incoming protocol used.

So in essence each email account is two accounts, one incoming and one outgoing. That server name looks suspiciously like that used by a hosting company. Are your email accounts on a hosted site?

I looked at digital pacific and they have these settings on their site for email https://support.digitalpacific.com.au/en/knowledgebase/article/general-email-settings

Those server names and the ones in your error do not look like they will ever matchup. So what exactly is in outgoing server (SMTP) for your accounts that are not working? There needs to be an entry in there for all three email addresses used with the correct username and password for the email address.

Thanks for that, Matt.

The server name is indeed from a hosting company and they are the ones that host my email. They sent me the email settings when I complained about not being able to send emails. They are the same as they always have been.

When I started Thunderbird just now, it sent an email from the unsent messages that had been there for a couple of days. Other test emails from the two accounts that haven't been working also went without a problem! So at the moment they're working again.

The speed of the internet here is not great. Would that make any difference? That's the only other thing I can think of. Why would it work one day and not the next? Frustrating.

Hi Greg,

Some things to try :

The SMTP server in the error is listed as vmpc65.digitalpacific.com.au Is this just a description ? Even so maybe try changing it to the format specified in the info for your provider.

I would expect this should be mail.digitalpacific.net.au The name of the server should be here which is not specific to your email address

The company list their settings as : Outgoing Server: mail.yourdomain.net.au Encryption method: SSL SMTP Port: 465

Where your domain is I am assuming digitalpacific

If you are using the SSL encryption settings, have you tried enabling DNS over HTTPS in thunderbird ? and see if that helps ?

Hope this helps, some.

The speed of the internet here is not great. Would that make any difference? That's the only other thing I can think of. Why would it work one day and not the next? Frustrating.

Internet speed only becomes an issue when the message size is large and you have outgoing email scanning enabled (it significantly delays sending usually). With both those things you can experience timeouts on the connection, but those usually generate an error message as the timeout aborts the transfer that has commenced.

However sometimes outgoing scanning messes up the connection and a newer version "just gets installed" and the problem goes away. (Think Crowdstrike, they released a very good example of a poor update, but these software updates that you are not even notified of are occurring sometimes daily with security software that is deeply embedded in your system.)

What is far more common is sending or receiving or both are blocked by antivirus products because the version of Thunderbird is new and their rather dodgy software firewalls have not received a note from home that Thunderbird has a new version, but I really do not think that was your issue as the server was contacted and refusing connection. This sometime is the result of too many incorrect password attempts say, which results in a timed lockout for a day or until someone at the provider lifts it.

But if it is working, lets just leave well enough alone.

It's stopped working again today! Grrr.

Jenny, the settings that digitalpacific recommend are: vmcp65.digitalpacific.com.au/mail.[my domain] However, Thunderbird says that's not a valid server name.

Yesterday and in the past it has worked with just vmcp65.digitalpacific.com.au My user name is my email address with my domain. Port 465 Normal password SSL/TLS