BT are blocking the complete domain which the sender is sending from. Rachel Rickard Straus, Financial Mail On Sunday This sounds fiddly, but isn't necessarily. Comic should be in the grade given in the listing title. You should check that you are complying with this link and if you are you will need to contact the BT Postmaster. I am not receiving emails to my Metronet account from at least two contacts with btinternet email addresses. All incoming emails were there on my phone, but when trying to send an email, I got the same error as Shortm showed in his first post. The account I am using is Gmail (the google mail). In the last 24 hours I have been unable to send any mail from my@btinternet.com account from any of my devices. When I ran Connection Doctor (available in Mail/Window/Connection Doctor) my btinternet connection showed green (OK) but I noticed that the SMTP connection details said "login not required". Thanks I decided to wait and see and this evening emails are sending OK again with the exception of one email that returns a 453 Too many recipients error message - I was trying to send an email to about 50 people on Thanks for the examples that have been provided so far. The "Port" was set to 587 (correct) and "Use TLS/SSL" was checked (correct) but "Authentication" was set to "None". Uninstall and Reinstall Mail app A. Uninstall - Windows Key+X > Click Windows Powershell (Admin) > Copy the below and paste into Powershell and Enter Sadly not the same as my experience. For email, I use Microsoft Outlook (from Microsoft Office, not outlook.com) email on my Samsung S10 phone and on my laptop. Reset Mail app Right click on Windows Start > Apps & features > Scroll down and click Mail & Calendar > Click Advanced options > Click Reset > Restart your computer 3. Solved: Unable to send email from Outlook app - BT Community mingoslkd, call My two contacts on btinternet.com have asked a number of times if I have received their emails, and I haven't.