I have been troubleshooting this for days and I haven't been able to figure it out. We have a SBS2000 server behind a firewall, email/webhosting done by 3rd party, dynamic IP from ISP(sbc). Outlook clients are configed for exchange and POP3 to get outside email from host.
The problem is with the outgoing email. Most outgoing email seems to flow just fine, but some end up as an unreachable destination with the user getting NDR message. Sometimes when the user gets an NDR message the email actually went through but most of the time it doesn't.
I have tried making changes to the default SMTP virtual server and creating an SMTP connector but the problem persists.
I REALLY need some help with this.