Way to make Thunderbird flag if you have more than one email in the To field?

Hi.

Happy New Year everyone!

On New Years Eve, I sent many emails but put them in the To field separated by a comma (like in the attached image). I meant to put them all in the Bcc section but forgot.

Is there a way to make Mozilla Thunderbird flag if you have more than one email in the To field? Just like it flags you when you omit to put something in the Subject field or fail to add an attachment after you mention the word 'attachment' in the body text?

Thanks.

 

Thank you very much DavidGP.