Can't send mails to some domains

[nicolaas1]

I have since yesterday a strange problem:

We can't send to a selection of domains. While others are just fine.

These are the error messages i get from the que:

An SMTP protocol error occurred

and

The specified network name is no longer available

Can someone help us with this ?

Thanx

 

[cjweaser]

I would check on the SMTP ports that you're using. Contact your ISP for any SMTP issues. Find out from them is they have any other SMTP Ports to may use aside from the default ones.
Other way to resolve this, is use an SMTP relay, like this one, give it a try it's free for up to 30 days, easy to setup in Exchange =>

http://www.dnsexit.com/

Hope this helps.