Apple Mail Creating Hundreds of Email Error Message Windows: This message could not be sent.

micksieben,

It's great you were able to narrow it down to the Gmail account. If you visit the online Gmail webmail portal, do you show anything in your Outbox there that isn't able to send? If not, we recommend reaching out to Gmail support to help check things on their side.

Let us know how that goes.

Take care.

Hey micksieben,

We understand that you're having an issue with a pop-up appearing for your outgoing mail server. Removing and adding the accounts back was a great first step. When adding the accounts back, when did the alerts start again? Does it seem to be tied to a particular account, either iCloud or Google? The following steps may help to resolve this: If you can’t send emails in Mail on Mac

You mention thinking this could be coming from a calendar. Have you checked for possible spam event: Report a junk calendar event invitation on iCloud.com

Keep us posted.

Take care.

Mick,

It's odd it continues after removing the account. Were you able to check your Google account too for possible spam invites as mentioned earlier?

We also recommend signing in to your Google account using their webmail portal to see if anything is showing in the Outbox. If the issue is fully isolated to the Google account, as you mentioned earlier, we recommend reaching out to them to see if there's something happening on their side.

If not, does this happen in a new user account: Set up users, guests, and groups on Mac

Keep us posted.

Take care.

Hi Mario, thanks for writing! It seems to be tied to my Google Calendar.

The minute I added the gmail account back it triggered all the alerts unable to be sent.

How can I remove that?

Thanks, M