Question : SBS2008 Mail delivery delays

I have a small network with a single SBS 2008 server running exchange.  Recently we are having issues with mail not being recieved until several hours after it was sent by outside senders.  For the most part, internal e-mail within the exchange organization is working OK.  It seems to be only happening with external messages.  Do you have any suggestions for tracing this issue down???

Any assistance would be appreciated.

Answer : SBS2008 Mail delivery delays

I TRIED TELNETTING YOUR SMTP SERVER  BUT UNFORTUNATELY I COULDNT CONNECT

I SUSPECT PROBLEM IN YOUR FIREWALL R WITH YOUR SPAM SECURITY SOFTWARE