The Answer

By Larry Seltzer  |  Posted 2005-05-19 Print this article Print

: Port 587"> The real answer for most people is port 587. It turns out that this port has always been there and under the applicable standard is actually the preferred port:
    3.1. Submission Identification
      Port 587 is reserved for email message submission as specified in this document. Messages received on this port are defined to be submissions. The protocol used is ESMTP [SMTP-MTA, ESMTP], with additional restrictions as specified here. While most email clients and servers can be configured to use port 587 instead of 25, there are cases where this is not possible or convenient.
      A site MAY choose to use port 25 for message submission, by designating some hosts to be MSAs and others to be MTAs.

Most, and probably almost all mail server software supports authenticated submission on port 587. Any that dont are non-compliant and you should complain. Its essential that if you add port 587 support it enforces authentication; otherwise youre just trading off port 25 vulnerability for port 587 vulnerability.

On the assumption that most of the situations wherein external access is a problem involve hosted domains, I asked several of the largest hosting services whether they support port 587 access for external users to hosted mail domains. Remember, just because their servers support it doesnt mean the hosting service opens the port on the firewall and enables it on the mail server. Here are the answers I got or didnt get ("yes" means they support port 587 for external users):
  • 1and1: yes
  • Interland: yes (not just a fallback; their docs tell users to use 587)
  • ThePlanet: "The Planets mail service does not currently advertise a submission service on TCP 587 by default, and weve never received a request to do so."
  • EV1: No response
  • Yahoo! Domains: No response (but I think the mail is managed by SBC, which supports port 587 on its own accounts
  • GoDaddy: No response
  • Verio: "As a business ISP, Verio does not block port 25 mail for its customers, but in many cases does enable alternate ports so that customers may continue using their servers for mail. The majority of server plans at Verio supports port 587—some by default. Our dedicated hosting customers can enable or disable as they require."

So its a mixed response. I think its cheesy for a major ISP not to support it, but I suspect ThePlanet is right that there isnt a lot of clamor for it. There should be, and users need to know that there is a relatively easy answer for the "problem" of ISPs blocking their port 25 access.

Its inevitable that malware writers will work around authentication solutions by cracking cached credentials, but this still leaves the ISP in a powerful position, since it will see the spam going through its servers and will be in a position to easily block the user and force them to remediate.

Users like me who have good protection against spam and viruses can easily overlook them, but they are still a major problem. Its frustrating that there is so much opposition to solutions to them, even if the solutions are far less disruptive than the problems. The answer could be within our reach.

Security Center Editor Larry Seltzer has worked in and written about the computer industry since 1983. Check out eWEEK.coms for the latest security news, reviews and analysis. And for insights on security coverage around the Web, take a look at Security Center Editor Larry Seltzers Weblog.

Larry Seltzer has been writing software for and English about computers ever since—,much to his own amazement—,he graduated from the University of Pennsylvania in 1983.

He was one of the authors of NPL and NPL-R, fourth-generation languages for microcomputers by the now-defunct DeskTop Software Corporation. (Larry is sad to find absolutely no hits on any of these +products on Google.) His work at Desktop Software included programming the UCSD p-System, a virtual machine-based operating system with portable binaries that pre-dated Java by more than 10 years.

For several years, he wrote corporate software for Mathematica Policy Research (they're still in business!) and Chase Econometrics (not so lucky) before being forcibly thrown into the consulting market. He bummed around the Philadelphia consulting and contract-programming scenes for a year or two before taking a job at NSTL (National Software Testing Labs) developing product tests and managing contract testing for the computer industry, governments and publication.

In 1991 Larry moved to Massachusetts to become Technical Director of PC Week Labs (now eWeek Labs). He moved within Ziff Davis to New York in 1994 to run testing at Windows Sources. In 1995, he became Technical Director for Internet product testing at PC Magazine and stayed there till 1998.

Since then, he has been writing for numerous other publications, including Fortune Small Business, Windows 2000 Magazine (now Windows and .NET Magazine), ZDNet and Sam Whitmore's Media Survey.

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