Sending of the message failed. The message could not be sent

[goldered]

Dear thunderbird support,

I keep getting this error 'Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.office365.com timed out. Try again.'
But not every time. Only sometimes. And sometimes it gives the error but sends the message successfully anyway. It is getting really frustrating. It only started a few days.

1) How to solve this issue of intermittent timeout issue? Because If I get that pop up error it takes over the entire thunderbird and stops sending later messages that I've scheduled by send later add on.
2) Is there a way to remove that popup and just ask it to try again like 5 or 10 minutes later? Rather than give that nasty popup and just take over the entire thunderbird.

Thanks.

[DanRaisch]

Seeing that the error appears only intermittently with no changes in Thunderbird, it sounds as though the issue is not in Thunderbird but either on the server end or in the network in between you and that server.
How is the account set up, as POP or IMAP? In Thunderbird the menu path is Tools->Account Settings->Server Settings->Server Type at the top right of the dialogue.
How are you scheduling messages to be sent later? Are you using an extension like "Send Later" ( https://addons.thunderbird.net/en-US/th ... d-later-3/ ) or are you using menu patah File->Send later (or key combination Ctrl+Shift+Enter?