Thank you for replying! I've checked all the settings and they match what you've put above, I've also tried removing all the passwords and re-entering them on start up but emails still won't send! It's so frustrating!!

re : I've checked all the settings and they match what you've put above

You have not got the same as advised and as stated on website info. https://www.heartinternet.uk/support/article/how-do-i-set-up-a-mailbox-using-imap-on-my-device-or-mail-client.html

According to the image you posted, you have this: smtp.hawkstonecars.co.uk

but advise from both the website and sfhowes says use this: mail.hawkstonecars.co.uk

Suggest you modify your outgoing server settings.

Hi, Thanks for that, I'm useless with this type of thing. I've done that and am still getting the same error message as shown in the second image shared.

The loss of connection it not a timeout. Thunderbird actually reports timeouts as such.

My guess is you have an anti virus product scanning your mail and it is making a complete hash of it, although there are other reasons. That is a good one to check first.

Ah ok, that might be it. How to I stop it from making said hash? I've gt Microsoft Security Essentials on the laptop.. Thank you!

The problem has now been solved, it was an issue regarding the outgoing server settings, the email host provider has sent me the correct details. Thank you to all contributors for all your help.