my send button is grayed out & I can't send emails

i know its a bit late, but for anyone in the future, i had the same but couldn't find connection doctor.

it turned out, after hours of searching for a missing e-mail that it was actually still there and unsent, on closing mail hit popped up again !!

In Mail's Window Menu, choose Connection Doctor, any red dots for status, if so what is the message?

Then click the Show Details button & Check again.

Any luck yet?