Problem setting up emails on new Mac using OS Sequoia

[#1]

Also have a read of this - https://discussions.apple.com/thread/254457126?sortBy=rank

[#2]

Morning! Still no luck. I will read the information on the link you sent me.

[#3]

Hello. Well I finally managed to get my emails! The email set up instructions on Plusnet state,"The username and password for your main (or first) Plusnet email address are the same as your account username and password". This is not the case. I tried an old password and it worked. 

Thank you so much for taking the time to help me.

Kind regards

Annie

[#4]

Do not know how you fixed this but that statement is absolutely true … except when your email account has been compromised and Plusnet’s security measures change the email password.

The account and primary email passwords are the same, except as stated above. In those circumstances you must change the ACCOUNT password to regain access to the email address.

Secondary mailboxes have their own separate passwords. So the consideration here is your email address the primary mail account or a secondary one?