MS Exchange Sending E-mail not working

I am using eM Client 7.0.26687.0 … For some reason I am not able to send emails. I get an error message. I use another mail client and I am able to send emails so the error message that I am getting doesn’t make any sense.

This started happening to me as well.  I have several emails sitting in the outbox but I keep getting the same error as shown above.

Hey, this is happening to me also, since a a week. Please i need help

Is just happen with the big size messages, and looks like the receiver get the email,

Same thing with version 7.0.26861.0 have sent ticket to eM Client Inc still waiting for resolution

None of the messages I have sent have been that large.  I’ve even tried deleting some of the redundant and resent emails, but still nothing is going through. 

Nothing of my login changed but it I still get an error like above.