Using older versions of Outlook for Mac for personal email and calendar
Hi, Paul S
Sorry for this frustration. Here are some suggestions you can try:
Sign in to your email provider’s website and send a short message to yourself. If it fails there too, contact your email provider, or your workplace IT team if this is a work account. If it sends there, focus on Outlook on your Mac.
In Outlook, choose Help > Check for Updates, install any available update, then restart Outlook and try again.
If webmail works but Outlook still won’t send, first make sure any important unsent drafts are saved elsewhere. Then go to Tools > Accounts, select the account, and choose Manage > Reset Account. This resyncs Outlook, but it can remove items that haven’t synced to the server.
If it still fails, please share the exact error message and whether this is a work, Outlook.com, Gmail, or other account. That will help narrow down the next step without repeating the same checks.