I am the ISP, and we currently don't. However, I inherited this setup and have been slowly fixing glaring holes (those are fairly well gone now) and not so glaring one. When our new firewall gets in, I will be rolling in port 25 blocks on dynamic IP addresses. The static ips will be unfiltered. Customers may send outbound mail through our SMTP server, or connect via alternate ports to their SMTP server.
________________________________ From: Zhiyun Qian [zhiy...@umich.edu] Sent: Thursday, June 18, 2009 2:36 PM To: nanog@nanog.org Subject: Is your ISP blocking outgoing port 25? It has been long heard that many ISPs block outgoing port 25 for the purpose of reducing spam originated from their network. I wonder which ISPs are still doing so. I know comcast has been doing that but they cancelled it after many complaints. It seems to be the same case for Verizon. AT&T is the major one that I know of that is still enforcing this policy. But they said they can unblock port 25 upon request. I am not sure how easy it is. One simple way to test if your ISP is blocking outgoing port 25 is to try: "telnet mx2.hotmail.com 25" or "telnet gmail-smtp-in.l.google.com 25". If the connection fails, it could be due to the fact your ISP is blocking outgoing port 25, although it can also be other reasons such as local firewall configuration. Can someone perform the test and let me know result if possible? Thanks a lot! Regards. -Zhiyun ________________________________ This message may contain confidential and/or proprietary information and is intended for the person/entity to whom it was originally addressed. Any use by others is strictly prohibited.
