Email error message

I am trying to reply to and send emails this morning, but keep getting this error message
Your message was not delivered because the return address was refused.

The return address was (etc etc )

the etc etc is my actual correct email address. I am using windows mail, and xtra. Tried emailing xtra to ask, but don't think that went either. Looked on their webpage FAQ but didn't find anything helpful there. Is it likely to be them, or me?

The same thing happened to me this morning! Not what I need right now!!!!

Seems to be back up and running again tho.

Yes, you'll have a lot to do right now! You did tell me there was going to be an ATM on site, or did my erratic brain dream that bit up?

Ummm.... sorry, but your dreaming that bit