Maybe, if you post a screen shot of your SMTP server settings, some suggestions may be made.

Thank you David, here is a shot of the settings. But I am having the same problem with both of the e-mail accounts I use with Thunderbird and the SMTP settings are different for both of them. I am hoping that if I can get the problem sorted out on this one then maybe the other will start working too.

Okay, now you say there are two accounts that don't work. And you're saying there is no error message of any kind? Not knowing the email provider, I suggest changing port from 587 to 25 and put your complete email id in as user, not just tonydxn.

Yes, two accounts, same problem on both, no error messages at all on either of them. I made the changes you suggested, but there is no difference.

Perhaps the issue is your setup is not complete.

Starting with the description. As this is the human readable entry for you to confirm the correct SMTP server is used with the correct mail account. It is mandatory. Even if the machine can work without it. You can not confirm settings are correct in account settings.

Password: I understand from the plusnet web site a password is not required it is optional, if you are signed into the internet using their service. Use one anyway. You never know when you might find yourself connected via a neighbors WiFi by accident or in the case of a tablet or laptop at an internet hotspot in a train station of a cafe. That should not be the source of random email issues, but without a password it will be.

Connection security: The plusnet web site says STARTTLS your setting is none. Not going to work that way.

They even go so far as to say if your can not use STARTTLS but SSL/TLS insted to use port 465. As your provider is asking you to use STARTTLS, an encrypted connection on the port you have set. I suggest you do as they ask.

As a general rule mail settings are a lesson in copying what the provider tells you to use. Plus net have their setting published here. Where they offer this somewhat confusing bit of advice

If you've been with us a while, your domain might be '.force9.co.uk or '.free-online.net'. If so, change '.plus.net' to '.force9.net' or '.free-online.net' for both your incoming and outgoing servers.

An encrypted connection might give some antivirus products a fit as they can't scan your connection unless you step though a load of hoops reducing your inherent security so they can scan outgoing mail on a system they say is clean. But that is beyond the scope of this forum.

Hallo Matt

Many thanks for taking so much time and trouble with my problem. I'm actually struggling to understand some of it, but I'm going to get the chap who set up my new computer to take another look at it before I get into your suggestions in depth. I suspect something about the way the computer is set up may be causing the problem.

I'll post again if necessary.

The reason you cannot send is because most of your smtp server settings are incorrect and not as advised by plusnet.

A Plusnet email address looks like this: something@username.plus.com.

SMTP server Settings:

• Description : enter username
• Server Name: relay.plus.net (NOT relay.plus.com)
• Port : 587
• Connection Security: STARTTLS
• Authentication Method: Normal Password
• User Name: username part of email address