If your network uses Microsoft ISA Server as a firewall/proxy, you need to create two packet filter rules to allow POPcon's traffic through.
Packet filters to create
POP3 filter (incoming mail retrieval)
- Protocol: TCP
- Direction: Outbound
- Local port: Dynamic
- Remote port: 110 (or 995 for POP3-SSL)
SMTP filter (delivery to Exchange)
- Protocol: TCP
- Direction: Outbound
- Local port: Dynamic
- Remote port: 25