Search Again: Re: MX and CNAMES revisited, listservs From: billc@greenbuilder.com Date: Wednesday, April 19, 2000 Time: 7:56:25 am >At 11:55 PM -0500 4/18/00, billc@greenbuilder.com wrote: >>Hi folks, >> >>A month or so ago I learned that MX records shouldn't be CNAMEd. So I went >>through and changed all my records. >> >>Now I'm wondering about my listservs. >> >>Part of the reason I'm wondering about it is that I want to set up a >>secondary mailserver to hold mail in the event my listserv machine goes >>down, and deliver it once it comes back up. I have a similar setup for my >>mailserver, and would like to use the same mailserver as the secondary list >>machine. If the relevant part of my setup is: >> >>greenbuilder.com. MX 10 mail.greenbuilder.com. >>greenbuilder.com. MX 20 mail2.greenbuilder.com. >>mail.greenbuilder.com. A 216.171.28.121 >>mail2.greenbuilder.com. A 216.171.28.3 >>lists.greenbuilder.com. A 216.171.28.120 >> >>where mail2 is the backup for mail1, can the listserv just get a second >>line that says: >> >>lists.greenbuilder.com. A 216.171.28.3 >> >>with the appropriate settings in the mail2 server to hold and send? Should >>lists.greenbuilder.com be treated as an MX, since it is essentially a mail >>server? What about the CNAMES that point to lists.greenbuilder.com - they >>appear to be working just fine, but then again I had not seen any problems >>with the CNAMEd MX records either... >> >>I once thought I knew what I was doing. Now I'm not so sure. ;-/ Chris Buxton cbuxton@menandmice.com replied: > >You should not add the second A record for lists.greenbuilder.com. >You should instead add the following MX records: > >lists.greenbuilder.com. MX 10 lists.greenbuilder.com. >lists.greenbuilder.com. MX 20 mail2.greenbuilder.com. > >CNAME records that resolve to lists.greenbuilder.com will not cause >any problem and should work fine, so long as they don't appear in an >MX record. If you want to add MX records for lists.otherdomain.com, >have those MX records resolve to lists.greenbuilder.com and >mail2.greenbuilder.com. Wait a second. I get the part about MX for lists. But in that previous conversation, I asked >>Someone over on the SIMS list who usually knows what he's talking about >>just stated that pointing MX records to CNames is a big time no-no, won't >>work, half the net won't understand, is counter to DNS specs, etc etc. >> >>Here's what I was talking about: >> >>> domain1.com MX 10 mail.domain1.com >>> mail.domain1.com C mail.mydomain.com >> >>Now, I've been doing that for a while already, with no known problems. >>This makes it much easier should I ever decide to move the IP of the main >>server (mail.mydomain.com). That's been known to happen. >> >>So am I wrong, or is he? >> And got the reply from Jerry Pasker-Systems Admin." <info@n-connect.net> on this list, as well as similar replies on the SIMS list: > >You're wrong... CNAMES in MX records break things quite badly. I've run >into it myself once and after trying to figure out why SOME (two acutally) >mail servers were not being able to send mail to my domain, I traced it to >me placing an MX record that pointed to a CNAME. It worked fine, until I >changed the name of my mailserver, and without thinking about it, made a >CNAME of the old server name point to the new name, without changing the MX >records. At that point the MX records that once pointed at A records, >were then aimed at CNAMES, and things started getting weird. > Ok, so is the following kosher? greenbuilder.com. MX 10 mail.greenbuilder.com. greenbuilder.com. MX 20 mail2.greenbuilder.com. mail.greenbuilder.com. A 216.171.28.121 mail2.greenbuilder.com. A 216.171.28.3 lists.greenbuilder.com. MX 10 lists.greenbuilder.com. lists.greenbuilder.com. MX 20 mail2.greenbuilder.com. lists.greenbuilder.com. A 216.171.28.120 and then on client's domain records, have: domain.com. MX 10 mail.domain.com. domain.com. MX 20 mail2.domain.com. mail.domain.com. A 216.171.28.121 mail2.domain.com. A 216.171.28.3 lists.domain.com. MX 10 lists.greenbuilder.com. lists.domain.com. MX 20 mail2.greenbuilder.com. Can/should that instead be: domain.com. MX 10 mail.greenbuilder.com. domain.com. MX 20 mail2.greenbuilder.com. lists.domain.com. MX 10 lists.greenbuilder.com. lists.domain.com. MX 20 mail2.greenbuilder.com. so that in the event that I move the mail servers to different IPs, I don't have to change A records for every domain? TIA BC Bill Christensen billc@greenbuilder.com Green Homes For Sale/Lease: http://www.greenbuilder.com/realestate/ Green Building Pro Directory: http://www.greenbuilder.com/directory/ Sustainable Bldg Calendar: http://www.greenbuilder.com/calendar/ Sustainable Bldg Bookstore: http://www.greenbuilder.com/bookstore

Messages In This Thread: MX and CNAMES revisited, listservs by billc@greenbuilder.com on Apr 18, 2000 at 10:00:14 pm Re: MX and CNAMES revisited, listservs by Men & Mice Support on Apr 19, 2000 at 2:53:23 am Re: MX and CNAMES revisited, listservs by billc@greenbuilder.com on Apr 19, 2000 at 7:56:25 am Re: MX and CNAMES revisited, listservs by Men & Mice Support on Apr 19, 2000 at 8:17:24 am