Strange Outlook, Outlook Express Errors


Well-Known Member
Aug 18, 2001
I have had 2 different customers complain about the exact same issue now, and I am starting to think it's not MS that's the problem. When trying to send email from either Outlook or OE, they get the following errror:

There is an unknown error. Subject &My Subject', Account: '[email protected] *', Server: '999.999.999.999', Protocol: SMTP, Port: 25, SSL: No, Errornumber: 0x800CCC0B

That error number (0x800CCC0B) has no real information for it.

Does anybody know what causes this and, more importantly, how to fix it?


Well-Known Member
Aug 13, 2001
Their ISP may be blocking port 25 as a lot of them are starting to do.

To check, have your client do the following:

from a DOS prompt, telnet to their IP address and tack a 25 at the end.

For example,
telnet 25

If they get a 220 welcome screen identifying the server, then there is a different problem.

If they get connection refused, then they cannot send mail through the server and they need to send it through their ISPs mail server. There is nothing you can do short of putting the SMTP server on a different port, but that would mean that all of your users will need to place a new configuration in their mail clients, and that is a bad workaround. They can still use the reply-to field on their email so anyone that gets email thinks that it is coming from their domain. Only the few people that actually look at all the headers will be able to tell.


Well-Known Member
Aug 17, 2001
Yea, it sucks that a lot of ISP's are not allowing outgoing SMTP from other providers. I guess they just have to these days because of spam. GRrrrrr. :(