I have been using a Blueyonder email address for 20+ years. The last couple of days I have not been able to send email via my iphone or desktop PC (Outlook), although I can still receive email. I get the error message "Cannot Send Mail: The Username or Password is incorrect". So I go into Settings and retype the Password. This doesn't fix it. I know it is the right Password because I can still access my blueyonder emails via the Virgin Media webpage (on which I can still send emails, incidentally).
So here's the weird thing. When I switch off wifi on my phone and try sending an email via 4G it goes through with no problems. So it seems there is something wrong with the blueyonder outgoing-wifi link. I live in a rural area and access wifi via wireless broadband and 4Gee router. I only recently moved here but everything worked fine for a month or so.