Very unusual error message

[TonyO]

Since last night I have been unable to send mails. I keep getting the
following error message:

Your message did not reach some or all of the intended recipients.



Subject: Test 11

Sent: 19/02/2008 19:59



The following recipient(s) cannot be reached:



'(e-mail address removed) 19/02/2008 19:59

503 valid RCPT command must precede DATA



(e-mail address removed) 19/02/2008 19:59

503 valid RCPT command must precede DATA



My internet search provided solutions that did not work.

My ISP / Administrator does not know what to do.



Can you help?

 

[TonyO]

Without "doing anything", my problem looks like it has gone away.

I am now sending emails without error messages!

Wonders will never cease...