SNDDST not sending to all email addresses

["John Allen" <jallen@xxxxxxxxxxx>]

Hello everyone,

 

We have been using the SNDDST to send documents internally and to a few
customers. Everything has been working fine until yesterday.

Starting yesterday the emails we send internally (or corporate email
addresses) get delivered just fine. But the emails we are sending to 

our customers are not arriving at the customers location.

 

My Network people say they have not changed anything (but don't believe
everything you hear)

We are running V5R1

 

I have searched the archives and there are a lot of past posts on SNDDST but
I could not find anything that points me where to start trouble shooting
this.

 

Does anyone have any suggestions on where I should start looking to resolve
this?

 

Thanks in advance for any help you furnish

 

Allen