The error is:
U_ms_item_email_ews.uf_send: Error calling external object function sendandsavecopy at line 146 in function uf_send of object u_ms_item_ews.
The server cannot service this request right now. Try again later.
This error is coming back from the mail server that is configured within Profile. From Profile Support there will be limited support we can provide to resolve this issue. From previous cases, we have found that this error is usually caused when users have exceeded mail limitations set on their mail server.
Depending on the settings in place on the mail server, this issue will resolve itself once the mail server allows more requests. We would recommend reaching out to your email provider to find out what limitations each user has.