SNDDST problem emailing internally

["John Allen" <jallen@xxxxxxxxxxx>]

I know this has been covered before, and I have read through many messages
in the archives but have not found the solution.

I have set up our AS/400 to use SNDDST and I can send emails to people
outside of our domain (such as georeg@xxxxxxxxx or frank@xxxxxxx)
But I cannot send emails to anyone in our company (example to myself)

I see in the archives that I should try to telnet to our mail server and I
attempted that. I get a message:
sosrv35.dfw9.maint.ops.us.uu.net ESMTP not accepting messages              
I cannot find in the archives what this message means (I am not a telnet or
SMTP guru)

Can anyone point me to the next step I should take in trouble shooting this.
1) Why can I send emails outside but not within our company
2) What does the telnet message mean?

Thanks for any assistance you have to offer

John