This problem has been going on for years, it just comes and goes and nothing gets done about it. Not much help I'm afraid, just consolation that you aren't being singled out.
Thank God I am not the only one! Randomly I will get the message, 'The user or password for firstname.lastname@example.org is incorrest', which is complete rubbish. However, when I get this message I cannot send any emails. Is no one trying to sort out this issue, which appears to have being going on for a very long time?
Same problem here, and no idea how to deal with it. My settings are all correct, but I've been unable to send from my btinternet.com account all day.
same here for at least a week now - no solution from with MS or BT in sight. I get no error messages - indeed the email shows as 'sent' in outlook but nobody gets the emails. I am using a different email address via outlook without any problems. Sending an email via btinternet from my mobile phone works = does this means its the SMTP server? I dont know - I have posted similar elsewhere on here - yesterday.
I do not think it is Outlook - i think the problem is deep in BT