You need to enter your full talktalk.net email address as the Username or the SMTP mail server will not authenticate your sending. The mail app will indicate that the Username is optional. It's not.
The TalkTalk.net email settings you need are:
|Account Type||IMAP (recommended)|
|Incoming mail server||mail.talktalk.net|
|Outgoing mail server||smtp.talktalk.net|
|Authentication||Yes, Normal password
Hi Bludog, if Gondola's advice get this sorted for you please mark the post as best answer to reward the effort.
The screenshot is showing me an insecure authentication tick box. That's not the normal setup for a talktalk.net mail account.
Normally, I'd expect to see secure authentication, a TLS certificate appropriate for TLS 1.2 and a sign in with the normal password.
Can you show me the Server Settings tab please. NB for your security please image edit to obscure the first or local part of your email address.
Hi Bludog, Gondola will get you sorted of that I have no doubt. If there's anything that needs my input Gondola will let you and I know. Please let us know how you get on.
On the Server settings tab
(1. I may have confused you by asking you to image edit out the first part of the email address).
On the Advanced tab
All of the settings look good and I see the logs now report that there's a connection to the SMTP server so that's one step forward.
But the mail server is rejecting the password that Apple mail or Apple keychain is presenting. So, just check the password does work in TalkTalk Mail and you can send to yourself from TalkTalk Mail without any error message coming up. Then update the saved password in Apple mail / Apple keychain.
I was confident that removing the previously saved keychain password(s) and entering a proven password would work.
Which means that I'll ask if you're ok continuing troubleshooting with a different email client on the MAC to determine if that works ok?
If your MAC meets the system requirements for Thunderbird I'd suggest downloading the Thunderbird email client to set up an IMAP mail account as a test. Setting up as an IMAP email account doesn't alter the mailbox just mirrors what's in the online mailbox.
If Thunderbird does work ok then that means you know the issue is with the Apple Mail / Keychain / icloud Keychain
Email Settings Email settings - IMAP and POP3