BT Email Error 550 – what it means and how to fix it

Seeing error 0x800ccc79 or 550 when sending email? These errors usually mean your email client isn’t authenticating correctly. Here’s what causes them and how to resolve the issue quickly.

This usually happens when your email client isn’t set up for SMTP authentication. SMTP authentication ensures only authorised users can send email through our servers.

To fix this, enable SMTP authentication in your email client settings. If you’re not sure how, see your email software’s help section or our setup guides.

SMTP settings

Outgoing Mail Server: mail.btinternet.com

Port: 465 (this may not be automatically populated on selecting SSL, so you'll need to check)

SSL Encryption: Enabled (but not STARTTLS)

Authentication: PLAIN

Username: your email address including the @btinternet or @btopenworld.com part

Password: your btinternet or btopenworld password

550 Recipient Not Authorised

If you're trying to send an email from an invalid email address, you'll get an Error 550 message saying: Server Response: 550 Recipient Not Authorised [recipient rejected due to no authorised destination groups].

Please check the following:

• The address you're sending from was spelt correctly when you set up your email account. For more information, see How do I set up BT Email on my computer or mobile device?
• It's 24 hours or more since the email address was created, as it may take our system up to a day to activate a new address.

550 unknown local user

There may be a problem with the address you're sending to. If you're trying to send an email to an invalid @btinternet.com or @btopenworld.com email address then you'll get an Error 550 message saying Server Response: 550 unknown local user.

If you're trying to send an email to a different mail server (to an email address that doesn't contain @btinternet or @btopenworld) then you may receive a Delivery Status Notification (Failure) email from the destination mail server.

Please check the following:

• The address you're sending to is spelt correctly.
• There are no service problems with the destination mail server.