Security Basics mailing list archives
Re: Mail Servers blocking BAD Helo
From: Brandon Lee <lee.bran () gmail com>
Date: Sat, 1 Jan 2005 14:46:59 +0800
Hi all, Thanks alot for the sharing of your experiences. Well, i guess i would have to drop that BAD HELO implementation in the form of business point of view. However, what kinda spam filtering do you guys think will be less resource intensive? Currently im using Spamassassin and its sitting together on the POP servers(as well as webmail), however, it seems that too much spam mails are clogging up the system resources. im currently using qmail(with FEH patch) + maildrop + vpopmail + spamassassin on the POP servers to d the filterings. The result of the previous trial did reflect a huge number of spam mails coming directly to the MX servers because we have setup a remote smtp server for our clients to sent out emails to avoid them using MS email client connecting to MX to send emails directly(which will also avoid MS email client's drawback of doing HELO with system name instead of FQDN. Last but not least, Happy New Year to you people. Regards Brandon On Thu, 30 Dec 2004 17:15:58 -0500, Roger A. Grimes <roger () banneretcs com> wrote:
In my experiencing, too many MTA's don't comply. Enforcing compliance resulted in too many lost legitimate emails over the last year for me, so I turned it off. I was surprised by how many large and popular MTA's don't comply, and surprised by how much email my company was missing because I stuck to my guns for a year. Not worth it. -----Original Message----- From: Anthony J. Cogan [mailto:anthony.cogan () thinkunix com] Sent: Thursday, December 30, 2004 1:44 PM To: brandon () xcodes net Cc: security-basics () securityfocus com Subject: Re: Mail Servers blocking BAD Helo Well the technical side of me says if they do not conform to the SMTP RFC's then it's the ISP's fault.... However, the business side of me says you must keep your customers happy, they are the ones thay pay your salary and all your toys. Even if it means not implementing something because another vendor isn't doing something right. If you are an ISP, your customers demand and should expect reliable e-mail communications. We have our SPAM filters turned quite high and blocking the majority of foreign countries, but we have a couple customers that require email to/from specific countries, so we have opened up those specific needs. If your customer can't receive e-mail from someone they wish to communicate with, they will leave your business for someone who will provide them the service. They don't know about, nor do they care about RFC conformity, they just want their e-mail. It's a delicate balance. brandon () xcodes net wrote:Hi People, Not quite sure if this is OT but would require opinions to assist me inmaking decision of whether to block "BAD HELO" at SMTP level. Below isa brief desciption of the situation: My company's mail server are reciving alot of spams with non-DQDN HELO greetings during the smtp conversation. We are using 2 front-end MX servers whcih does smtp routes to the relevant POP servers. We have actually tried to implement blocking of all helo greetings that are notin FQDN format on one of the servers and the result seems to be good. However, the only problem that we faced is there other other ISP ain't using FQDN in their HELO greetings. We do have a couple of clients who are complaining that they are unableto receive mails from certain ISPs, which from our checks in the SMTP logs, the servers are using "MySMTP1" sort of HELO greetings. Now my management are asking me on this issue if we should fully implement such feature across the other MX servers or should we withdraw such feature fully from the MX servers. From my readings on the SMTP RFCs, they have indicated that SMTP servers must configure itshostname to FQDN which will be used in HELO Greetings(if im not wrong).Im also wondering if there are any other ISP using such implementation(Blocking BAD HELO greetings) on their SMTP Servers, any idea? Would welcome all opinions on this issue. Thanks Brandon
-- rgds Brandon
Current thread:
- Re: Mail Servers blocking BAD Helo Brandon Lee (Jan 05)
- <Possible follow-ups>
- RE: Mail Servers blocking BAD Helo David Sherman (Jan 05)
- Re: Mail Servers blocking BAD Helo Brandon Lee (Jan 06)
- RE: Mail Servers blocking BAD Helo David Sherman (Jan 06)
- Re: Mail Servers blocking BAD Helo Sebastian@Helsinki (Jan 10)
- Re: Mail Servers blocking BAD Helo Ed Weinberg (Jan 11)
- Re: Mail Servers blocking BAD Helo Sebastian@Helsinki (Jan 10)