I have recently taken over the IT position at a small company. I do not have any networking experience and have been tossed straight into the fire.
The problem I'm having is with the email. The mailserver is running on Windows NT and is using Groupwise 5.5. There is also a Cisco PIX 501 for firewall. The only problem with the email is the outbound side. Internal and inbound emails work perfectly. Outbound emails work about 10% of the time. Senders will sometimes receive a message saying their email didn't go through due to the IP being banned or it is undeliverable or no response at all. The errors numbers I have seen are 550, 553, 571, and 554.
The Cisco Pix 501 IP address (18.104.22.168) is listed on the CBL. I do not know how to change any settings in the Cisco because the device manager never loads in IE. I have spoken with the previous IT manager and he had never seen this problem. He did say that port 25 is blocked except for the mailserver. From what I have researched it seems like this would fix my problem, but I've been told it was already done. Do I need to redo this? It is odd because their doesn't seem to be a pattern as to what emails are blocked.
I'm not sure what to do at this point and any advice is greatly appreciated.