Security Basics mailing list archives
FW: Mail relay question
From: "Nick Vaernhoej" <nick.vaernhoej () capitalcardservices com>
Date: Fri, 22 Feb 2008 12:26:44 -0600
Good day, So I am somewhat green when it comes to how mail gateways manage email. After finding that my own mail setup at home has caught almost 5000 spam mails in less than a month I have finally thrown my hands in the air and wanted to hopefully get some understanding from this list. The amount alone is huge I think when I am only hosting my wife and myself (as well as the usual abuse etc. contacts). I am worried that my home is an open relay in a manner I have not found. Then I learn that via telnet I can send email from mydomain.com to mydomain.com and have it delivered even when the telnet session is from a public IP. So, I am a little fuzzy on what it is I am trying to learn here, but: 1. Would you think 5000 emails a month with maybe 200 valid emails is normal in a home/family type setup? 2. Is mail always accepted and relayed when the sender and recipient domain is the same? (This is without sender authentication configured or capability). a. If yes, what is to stop an angry neighbor on his vacation to China from sending a nasty email from me to my wife? (In this unsecure setup). b. My gateway at home (Smoothwall using DSPAM/SEMF? mod) only accepts the initial HELO if followed by connecting domain name (HELO domain.com) So how come I can connect from domainx.com and send email from domainy.com to domainy.com? c. What can I do to remove this risk? 3. Any recommendations on a free mail gateway solution? SpamAssassin? ClamAV? My goal is to migrate away from Exchange 2003. I have been wanting to try Zimbra for mail server but would like a good mail gateway in the DMZ instead of hosted by the firewall. Thank you and I will follow up with answers to questions for clarification. Nick Vaernhoej "Quidquid latine dictum sit, altum sonatur." This electronic transmission is intended for the addressee (s) named above. It contains information that is privileged, confidential, or otherwise protected from use and disclosure. If you are not the intended recipient you are hereby notified that any review, disclosure, copy, or dissemination of this transmission or the taking of any action in reliance on its contents, or other use is strictly prohibited. If you have received this transmission in error, please notify the sender that this message was received in error and then delete this message. Thank you.
Current thread:
- FW: Mail relay question Nick Vaernhoej (Feb 22)
- Re: Mail relay question 0x90 (Feb 22)
- RE: Mail relay question Nick Vaernhoej (Feb 22)
- Re: Mail relay question 0x90 (Feb 25)
- Re: Mail relay question Aaron Howell (Feb 25)
- Re: Mail relay question Ansgar -59cobalt- Wiechers (Feb 25)
- RE: Mail relay question Nick Vaernhoej (Feb 22)
- Re: FW: Mail relay question Ansgar -59cobalt- Wiechers (Feb 22)
- Re: FW: Mail relay question Aaron Howell (Feb 22)
- RE: Mail relay question Ric Messier (Feb 22)
- <Possible follow-ups>
- Re: FW: Mail relay question rafael . almeida (Feb 25)
- Re: Mail relay question 0x90 (Feb 22)