email body not accepted with reason error 5.5.1 RCPT

1

I have a “email body not accepted with reason error 5.5.1 RCPT” error message, can you kindly help me out to resolve?

2

This is something to do with the encryption settings for SMTP.
I’m testing with an Apple Mac server 10.7 and although the diagnotic test works for SMTP with SSL on port 587 it gives error 5.5.1 when sending email.
If I disable SSL and use port 25 then it works. Not totally ideal as I would like the encryption.