Can’t send BTinternet email from new Outlook?

/01 — QUICK ANSWER

Can’t send BTinternet email from new Outlook? Start here

If your BTinternet email receives fine but won’t send in new Outlook, the outgoing (SMTP) server is nearly always the cause. The correct outgoing settings are mail.btinternet.com on port 465 with SSL, with authentication switched on and your full email address as the username — and because new Outlook often won’t let you edit those once an account is added, putting them right usually means removing the account and adding it back with the right details. Sending typically fails because the ‘server requires authentication’ box is unticked, or the port and encryption don’t match.

Receiving and sending use two different connections, which is exactly why one can work while the other doesn’t — you can read new mail through the incoming (IMAP) server even when the outgoing server is misconfigured. Below you’ll find the precise settings BT publishes, the common reasons sending breaks, and a step-by-step fix — plus an honest note on new Outlook’s known quirks with BT accounts. If you’d rather not touch server settings at all, call us on 01202 775566 and we’ll sort it remotely while you watch.

/03 — WHY IT FAILS

Why BTinternet sending breaks in new Outlook

Sending breaks for a handful of predictable reasons. Working through them in order usually finds the culprit:

• Authentication is switched off. BT rejects any message where the outgoing server isn’t authenticated, which typically shows as a 530 error. The ‘my outgoing server requires authentication’ setting must be on, using the same login as your incoming mail.
• Wrong port and encryption pairing. Port 465 needs SSL; port 587 needs STARTTLS. Mixing them — 465 with STARTTLS, or 587 with SSL — fails silently and leaves mail sitting in the outbox.
• You’ve left BT Broadband and dropped to free Basic email. When you leave BT, you have 60 days to move your mailbox to BT’s paid Premium Mail or link it to another BT Broadband line; otherwise it becomes free Basic email, which only works through BT webmail in a browser and can’t send or receive in Outlook at all. If that’s happened, no settings change will fix Outlook — you’d need Premium Mail or a linked BT line to restore email-app access.
• New Outlook’s IMAP quirks. Microsoft is still maturing new Outlook’s handling of third-party IMAP accounts — it won’t even let you edit the server settings once an account is added — so some BT users can receive but not send until the account is removed and re-added.

If your messages are visibly piling up, our notes on email stuck in the Outlook outbox and Outlook repeatedly asking for your password cover two of the most common symptoms.

/05 — STILL STUCK

If it still won’t send

Sometimes new Outlook simply won’t co-operate with a BT IMAP account, even with perfect settings. That’s a genuine, documented limitation rather than anything you’ve done wrong — several BT users find sending works immediately in Classic Outlook while new Outlook still refuses.

If you need to send today, the quickest workaround is to switch back: our guide on going back to Classic Outlook walks through the toggle. Classic Outlook gives you full manual control of the SMTP port and encryption, which is exactly what a stubborn BT account needs. You can also send from BT’s own webmail at bt.com in the meantime — that bypasses Outlook entirely and confirms your mailbox itself is healthy.

One caveat: if webmail works perfectly but no email app will send, and you’ve left BT Broadband, you may be on BT’s free Basic email, which is webmail-only by design — Outlook can’t use it until you move to Premium Mail or link the mailbox to a BT line. And if sending fails everywhere, webmail included, then the problem is the mailbox or BT account, not Outlook, and only BT can restore it. Our wider Outlook not sending emails guide covers the non-BT causes too. When you’ve tried the settings and you’re still stuck, that’s the point to hand it over to us.