Mail is not send emails

After upgrading my MacBook Pro M1 to macOS Tahoe, Im experiencing an intermittent ''sending Mail'' issue?.

I've re-installed the latest OS Tahoe, at least, twice on the advice of Apple Online Support...I've sent mail to my colleague, with the same domain as mine, and ''random person/s'' with other domains...the mail just ''sits there in Draft" Can someone help?