Sync error when sending emails using Outlook for Mac

Question

Sync error when sending emails using Outlook for Mac

Marla 170

I have been using Outlook for Mac for years, though my email provider is BT.

As of this morning, when I tried sending an email-no attachments, nothing: I got a sync error and the email got stuck in my Outbox. The sync error said: btprdrgo010.btinternet.com![Opens in a new window; external.](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7) Service not available.

This is very intermittent-some of my emails have sent while others are getting stuck in the Outbox. I'd like to know if this is a temporary glitch?

Marla 170 Reputation points

2026-09-27T08:24:57.02+00:00

Thanks for the above, AI! but all of my server settings are correct. This is a new error. I am attaching a screenshot here with the sync errors.

2 answers

Your answer

Marla 170 Reputation points

2026-09-27T08:24:57.02+00:00

Thanks for the above, AI! but all of my server settings are correct. This is a new error. I am attaching a screenshot here with the sync errors.

Answer 1

Hornblower409 16,200

@Marla said

my email provider is BT

If the checks on your Outlook client provided by the AI Answer don't help - It's possible the problem is a BT outage, or it may require that you work with BT Tech Support for a resolution. e.g.

[External Non-Microsoft Site] https://community.bt.com/t5/General-email-queries/BT-Email-account-and-Outlook-client/td-p/2443748

So as of sunday 14th September Outlook on a Windows 11 has stopped connecting to BT EMail, something that has been working for over 2 years seamlessly. The outlook client tries to connect but fails

Marla 170 Reputation points

2026-09-28T08:22:05.41+00:00

Thanks very much, Hornblower. In all my years with BT, and using Outlook for Mac, it's never been a BT outage issue. My web-based always functions as normal, when Outlook gives me grief. As it happens, I haven't had the issue since yesterday and hope that it was temporary, whatever the cause.
Marla 170 Reputation points

2026-09-28T10:13:41.3533333+00:00

This was a duplicate reply so have deleted.

Answer 2

A temporary server-side glitch is possible, but the supported checks for Outlook for Mac are:

Confirm the mail server is available. If Outlook previously worked and the error is intermittent, the mail server may be temporarily unavailable. Check with BT to confirm whether their outgoing mail server is having issues.
Verify Outlook is online. In Outlook for Mac, open the Outlook menu and make sure Work Offline is not checked.
Check the account settings. Go to Tools > Accounts, select the BT account, and confirm the email address, user name, and password are correct.
Check outgoing server authentication. In Tools > Accounts > select the account > under Outgoing server, click More Options, then verify the correct authentication type and credentials are entered. Some POP and IMAP accounts require SMTP authentication before sending.
If the network or ISP is blocking the outgoing SMTP connection, ask the provider or network administrator for an alternative SMTP server, then enter it in Tools > Accounts > select the account > Outgoing server.
If a message is stuck because it became too large, Outlook for Mac holds it in Drafts rather than Outbox. For messages with large attachments, remove attachments or delete the draft and permanently delete it from Deleted Items.

Since some messages are sending and others are not, the most directly supported explanation is intermittent availability of the outgoing mail server. If the issue continues after verifying Outlook is online and SMTP authentication/settings are correct, contact BT to confirm server availability or required SMTP settings.

References: