Chris Knadle wrote: > On Tue, October 12, 2010 7:18 pm, Frank D wrote: > >> ---- Allen <[email protected]> wrote: >> >>> On Fri, 2010-10-08 at 04:12 +0000, Frank D wrote: >>> >>>> - >>>> >>>> If I understand you right, you want to recieve mail on one of the >>>> >>> machines? Or are they going outside of your network? I'm pretty sure >>> you don't even need a MTA (mail transfer agent, ie sendmail) with >>> smartd, etc. if it's going to another machine. Though I've never had a >>> machine without an MTA, or looked to see exactly how they send mail.. >>> so I couldn't say for certain. >>> >>>> Frank DiMitri >>>> >>> Frank, it looks like you're correct. I happened to be reading today an >>> article called "Pernicious Ports" >>> http://www.berghel.net/col-edit/digital_village/dec-05/dv_12-05.php >>> >>> =========================================================================================================================================================== >>> >>> (2) Unix-Centric >>> >>> Most UNIX systems, regardless of brand, offer SMTP mail services through >>> TCP port 25. If the system is not actually a mail relay or server, then >>> you likely do not need this service running at all. The main exposure >>> lies in the failure to continuously patch the system. By the way, it is >>> a common misconception that an SMTP server must be running for a local >>> user or service to send email out of a UNIX box. This is simply not >>> true. The recommended solution is to block TCP 25 at the firewall. >>> >> SMTP is very simple, you don't need an SMTP server to SEND a message. Lots >> of programs/scripts will just do this themselves. Opening a TCP connection >> and setting up some basic stuff to send to a destination SMTP server is >> not >> hard. SMTP is a plain-text protocol. >> >> Some will pipe their output to a common program (I think 'mail' is used >> for this a lot) in order to send a message to another machine. I could be >> wrong about the program that's used. >> > > Yes 'mail' is one of the programs you can use to send an email; I've > occasionally used it to send an email within a script. However, don't > think that just because you CAN send an email without an MTA installed > that it's necessarily a good idea -- because without a 'real' MTA, there's > no retrying so on any error the email simply gets lost. If you need to > send an email and have the option of using a local MTA, do so. >
It is a testament to the application of Postel's Law (the part about being liberal in what you accept at least) that lets people throw just about anything at an SMTP service and have it get delivered successfully and unmangled. When you give the RFCs a look, you find there's a lot more rules to SMTP than one might gather from what lands in your mailbox (ex: the bare linefeed issue), but much like web browsers, MTAs have by necessity become extremely tolerant about having utter garbage thrown at them. - Ron _______________________________________________ Mid-Hudson Valley Linux Users Group http://mhvlug.org http://mhvlug.org/cgi-bin/mailman/listinfo/mhvlug Upcoming Meetings (6pm - 8pm) MHVLS Auditorium Nov 3 - Open Source Hardware: Bugs, Beagles and Beyond Dec 1 - IBM's Open Client Deployment Jan 5 - Building a Comunity Site with Drupal
