Having trouble with Emails not sending on Mail application

About 5 days ago I added two new email addresses to my MAC Mail settings.

A day later I noticed that my emails for all 6 of my accounts that I had sent were all sitting in the Outbox and not being sent.

These are with different hosting providers and I know it isn't a problem there and they are working fine from my mobile device. I can't seem to work out why this is happening and I'm not getting an error message when I try to send, they simply just sit in the outbox as if they aren't even trying to send.

I'm sure it's something simple I've done but 5 days later I still can't seem to work it out! Help please.....