MX/Zone/DNS question
I have a domain isbd.net which is hosted for me at BSNet where I have access to the zone file. I have added a CNAME record home[.isbd.net] which points at my home system (which has a static IP with a very long name). This works perfectly for me so far, I can access Web pages on the home machine's apache server at home.isbd.net and any port I open up is accessible as home.isbd.net. I have Postfix on my home system (for sending mail). If I want it to receive mail as well what do I need to do to the zone file[s]? At BSNet (where isbd.net has its zone file) will the CNAME entry I already have mean that mail for xxx@home.isbd.net will get sent on or do the MX records for isbd.net catch home.isbd.net mail as well? If home.isbd.net mail *is* sent on to my home machine do I need to do anything to the zone file there for it to accept the mail or will having Postfix listening on port 25 be all that's needed? (I suspect that *strictly* I should have a zone file with MX records on my home machine but that it may well work without) -- Chris Green (chris@halon.org.uk)
cl@isbd.net wrote: [...]
I have Postfix on my home system (for sending mail). If I want it to receive mail as well what do I need to do to the zone file[s]?
Short answer: it depends how your zone and Postfix are configured.
At BSNet (where isbd.net has its zone file) will the CNAME entry I already have mean that mail for xxx@home.isbd.net will get sent on or do the MX records for isbd.net catch home.isbd.net mail as well?
More likely the first than the second, but I seem to recall that some buggy mailservers handled CNAME badly.
If home.isbd.net mail *is* sent on to my home machine do I need to do anything to the zone file there for it to accept the mail or will having Postfix listening on port 25 be all that's needed?
Andrew Savory recently did something similar. See http://www.andrewsavory.com/blog/archives/001257.html (but Googlemail really does not rock). Hope that helps, -- MJ Ray - see/vidu http://mjr.towers.org.uk/email.html Somerset, England. Work/Laborejo: http://www.ttllp.co.uk/ IRC/Jabber/SIP: on request/peteble.
On Fri, Jan 26, 2007 at 09:22:40AM +0000, MJ Ray wrote:
cl@isbd.net wrote: [...]
I have Postfix on my home system (for sending mail). If I want it to receive mail as well what do I need to do to the zone file[s]?
Short answer: it depends how your zone and Postfix are configured.
At BSNet (where isbd.net has its zone file) will the CNAME entry I already have mean that mail for xxx@home.isbd.net will get sent on or do the MX records for isbd.net catch home.isbd.net mail as well?
More likely the first than the second, but I seem to recall that some buggy mailservers handled CNAME badly.
Actually not buggy behaviour - an MX should always point to an A record (part of the spec, IIRC), and hysterically, an A record was checked for, now the order is MX -> A -> undefined evilness!
If home.isbd.net mail *is* sent on to my home machine do I need to do anything to the zone file there for it to accept the mail or will having Postfix listening on port 25 be all that's needed?
Andrew Savory recently did something similar. See http://www.andrewsavory.com/blog/archives/001257.html (but Googlemail really does not rock).
Opinion, not fact (I have never and never intend to use Google mail, so I can not say wether it rocks or not - but I'd rather my mail wasn't indexed by Google, TYVM). Cheers, -- Brett Parker
On Fri, Jan 26, 2007 at 09:57:44AM +0000, Brett Parker wrote:
On Fri, Jan 26, 2007 at 09:22:40AM +0000, MJ Ray wrote:
cl@isbd.net wrote: [...]
I have Postfix on my home system (for sending mail). If I want it to receive mail as well what do I need to do to the zone file[s]?
Short answer: it depends how your zone and Postfix are configured.
At BSNet (where isbd.net has its zone file) will the CNAME entry I already have mean that mail for xxx@home.isbd.net will get sent on or do the MX records for isbd.net catch home.isbd.net mail as well?
More likely the first than the second, but I seem to recall that some buggy mailservers handled CNAME badly.
Actually not buggy behaviour - an MX should always point to an A record (part of the spec, IIRC), and hysterically, an A record was checked for, now the order is MX -> A -> undefined evilness!
... but that really doesn't answer my question. If there's an MX record (or MX records actually) for isbd.net does that have any relevance to mail for home.isbd.net? If it *doesn't* have any effect then what happens to mail for home.isbd.net - will the CNAME entry have any effect or will the mail just get rejected as having a non-existent destination?
If home.isbd.net mail *is* sent on to my home machine do I need to do anything to the zone file there for it to accept the mail or will having Postfix listening on port 25 be all that's needed?
Andrew Savory recently did something similar. See http://www.andrewsavory.com/blog/archives/001257.html (but Googlemail really does not rock).
Opinion, not fact (I have never and never intend to use Google mail, so I can not say wether it rocks or not - but I'd rather my mail wasn't indexed by Google, TYVM).
Not to mention that the above blog only talks about how to set up Postfix which I basically know anyway. What I want to know is whether I *have* to have MX and/or A records in my home machine's zone file or will things get there as a result of the CNAME record in isbd.net's zone file. -- Chris Green (chris@halon.org.uk)
On Fri, Jan 26, 2007 at 12:37:03PM +0000, cl@isbd.net wrote:
On Fri, Jan 26, 2007 at 09:57:44AM +0000, Brett Parker wrote:
On Fri, Jan 26, 2007 at 09:22:40AM +0000, MJ Ray wrote:
cl@isbd.net wrote: [...]
I have Postfix on my home system (for sending mail). If I want it to receive mail as well what do I need to do to the zone file[s]?
Short answer: it depends how your zone and Postfix are configured.
At BSNet (where isbd.net has its zone file) will the CNAME entry I already have mean that mail for xxx@home.isbd.net will get sent on or do the MX records for isbd.net catch home.isbd.net mail as well?
More likely the first than the second, but I seem to recall that some buggy mailservers handled CNAME badly.
Actually not buggy behaviour - an MX should always point to an A record (part of the spec, IIRC), and hysterically, an A record was checked for, now the order is MX -> A -> undefined evilness!
... but that really doesn't answer my question. If there's an MX record (or MX records actually) for isbd.net does that have any relevance to mail for home.isbd.net? If it *doesn't* have any effect then what happens to mail for home.isbd.net - will the CNAME entry have any effect or will the mail just get rejected as having a non-existent destination?
It *should* be rejected. -- Brett Parker
On Fri, January 26, 2007 1:13 pm, Brett Parker wrote:
On Fri, Jan 26, 2007 at 12:37:03PM +0000, cl@isbd.net wrote:
On Fri, Jan 26, 2007 at 09:57:44AM +0000, Brett Parker wrote:
On Fri, Jan 26, 2007 at 09:22:40AM +0000, MJ Ray wrote:
cl@isbd.net wrote: [...]
I have Postfix on my home system (for sending mail). If I want it to receive mail as well what do I need to do to the zone file[s]?
Short answer: it depends how your zone and Postfix are configured.
At BSNet (where isbd.net has its zone file) will the CNAME entry I already have mean that mail for xxx@home.isbd.net will get sent on or do the MX records for isbd.net catch home.isbd.net mail as well?
More likely the first than the second, but I seem to recall that some buggy mailservers handled CNAME badly.
Actually not buggy behaviour - an MX should always point to an A record (part of the spec, IIRC), and hysterically, an A record was checked for, now the order is MX -> A -> undefined evilness!
... but that really doesn't answer my question. If there's an MX record (or MX records actually) for isbd.net does that have any relevance to mail for home.isbd.net? If it *doesn't* have any effect then what happens to mail for home.isbd.net - will the CNAME entry have any effect or will the mail just get rejected as having a non-existent destination?
It *should* be rejected.
Since no MX record exists (unless you have wildcarded *.isbd.net) for home.isbd.net then mail will be routed to the A record for that host. You should not use CNAMEs with anything mail like.
From the sendmail docs:
"If no MX records are available for a given host, sendmail will try to send to that host directly. Once sendmail determines which host to attempt to send the message to: an intermediate host as indicated by an MX record, or a direct connection to the target host, it uses gethostbyname() to determine the IP-address of the target machine in order to make a connection." -Mark ----------------------------------------------------------- This message may contain confidential and/or privileged information. This information is intended to be read only by the individual or entity to whom it is addressed. If you are not the intended recipient, you are on notice that any review, disclosure, copying, distribution or use of the contents of this message is strictly prohibited. If you have received this message in error, please notify the sender immediately and delete or destroy any copy of this message.
On Fri, 2007-01-26 at 13:52 +0000, Mark Ridley wrote:
Since no MX record exists (unless you have wildcarded *.isbd.net) for home.isbd.net then mail will be routed to the A record for that host. You should not use CNAMEs with anything mail like.
From the sendmail docs:
"If no MX records are available for a given host, sendmail will try to send to that host directly. Once sendmail determines which host to attempt to send the message to: an intermediate host as indicated by an MX record, or a direct connection to the target host, it uses gethostbyname() to determine the IP-address of the target machine in order to make a connection."
I am not sure that would work if the senders MTA is something like Exchange "To determine mail hosts, the sending Exchange server checks for an MX record. Next, the sending server resolves the MX record to an IP address by checking for an address (A) record. If MX records for remote domains are missing, this may cause messages destined for the remote domains to back up in the Exchange server Remote Delivery queues in addition to other routing or service delays."
participants (5)
-
Brett Parker -
cl＠isbd.net -
Mark Ridley -
MJ Ray -
Wayne Stallwood