can't send email on my iphone 4s

I can't send email on my iphone 4s. I get an error message "A copy has been placed in your Outbox. The recipient (any email address I try) was rejected by the server because it does not allow relaying." I get the same message on all 3 email accounts I have on my phone. I can receive emails on all accounts, but cannot send.  I think it started after the last update.