Mail app not sending emails on iMac M1 after startup

I have a IMac 24" M1 2021 which has a problem every morning at startup and the first few emails I compose has the Send button greyed out and the only way to resolve it is to restart the machine, sometimes this requires three or four attempts. I have just updated to Sequoia 15.5 but the problem still persists. Any help in solving this would be greatly appreciated.

[Re-Titled by Moderator]