Outlook for Mac-Legacy-can't send emails-this same issue occurred a few weeks ago

Marla 170 Reputation points
2026-10-20T09:48:42.9333333+00:00

I am copying and pasting this issue as I had the same issue end of September:

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 errors and other pop ups all say that my password or username may be incorrect but I know this is not true because I am able to login to BT Mail on the web successfully. This is getting tedious as this is the second time in less than two months that this issue is arising.

Microsoft 365 and Office | Other

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  1. AI answer

    2026-10-20T09:49:01.77+00:00

    Since BT Mail works in the browser, the mailbox itself is likely available and the issue is in Outlook for Mac account or connection settings.

    Try these checks in order:

    1. Confirm Outlook is online
      • In Outlook for Mac, open the Outlook menu.
      • Make sure Work Offline is not checked.
    2. Verify the account credentials in Outlook
      • Go to Tools > Accounts.
      • Select the BT account in the left pane.
      • Confirm the email address, user name, and password are correct.
      • If the account still fails, the mail provider may require special settings such as SSL or non-default ports.
    3. Turn on SMTP authentication
      • This is especially relevant when mail is received or webmail works, but sending fails and messages stay in Outbox.
      • In Tools > Accounts > select the account.
      • Under Outgoing server, select More Options.
      • Choose the required authentication type and enter credentials if prompted.
    4. Check whether the network is blocking the outgoing mail server
      • If this started suddenly and happened before, the SMTP connection may be blocked by the current ISP or network.
      • In Tools > Accounts, select the account.
      • In Outgoing server, verify the server name/address.
      • If the current network or ISP blocks that SMTP server, an alternative SMTP server from the provider or network administrator is required.
      • This can vary by location, especially on a laptop moving between networks.
    5. Check for proxy requirements
      • If the network uses a proxy to reach mail services, configure the mail proxy in macOS System Preferences using the settings provided by the network administrator.
    6. Rule out a provider-side outage
      • If Outlook connected successfully before and suddenly stopped, the mail server may be unavailable. In that case, check with BT Mail to confirm server availability.

    If the main symptom is specifically messages stuck in Outbox, there is also a documented Outlook for Mac issue where resetting or renaming Outlook folders can resolve it, using either Outlook for Windows with Outlook.exe /resetfolders, Outlook Web App, or the Exchange admin cmdlet Set-MailboxRegionalConfiguration. Those methods apply only if that folder-state issue matches the environment.

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