Topic: DNS name for mail and web components

[rgmhtt]

I am setting up a replacement for my current, Scalix-based, mail server (and web server).

The system's hostname is z9m9z, as my ISP is a backup mailrelay (for when my link is down), I want to keep this as the mailserver's name.  Thus NOT use mail.domain.

So I will set up the system as z9m9z.domain.  I will NOT be running DNS (or DHCP) on the box, but point to my domain's DNS server.  In my DNS setup I will be leaving the mx records alone and just swapping out the boxes (actually I will build the SME version on another IP address, then once configured, swapping the boxes).

Any problem with NOT defining mail.domain in the DNS.  I note that server-manager allows me to remove this DNS entry if I am running DNS on SME.


Also this box will NOT be www.domain, another will, but I do want to allow webmail access, both locally and remotely.

And today is my chance to build this system.

[David Harper]

AFAIK so long as your MX record points to a valid A or CNAME record you should be fine. There's no requirement for the server to be called "mail".

[CharlieBrady]

AFAIK so long as your MX record points to a valid A or CNAME record you should be fine.

CNAMEs are not valid as MX records.

There's no requirement for the server to be called "mail".

Correct. There is also no requirement that SME server is even aware of the hostname which is used in global DNS to identify it as MX for the domain. The MX hostname isn't used in the SMTP transaction.

[David Harper]

CNAMEs are not valid as MX records.

Oops, my mistake! Thanks for the correction

[CharlieBrady]

The system's hostname is z9m9z, as my ISP is a backup mailrelay (for when my link is down), I want to keep this as the mailserver's name.

I don't see how your having a backup mail relay affects your choice of hostname. In any case, I'd advise you not to use a backup mail relay, as it reduces your ability to control spam without generating backscatter. Backup mail relays are unnecessary - sending hosts are required to spool the mail and attempt later redelivery.

[rgmhtt]

CNAMEs are not valid as MX records.

That one I know.   

I was pulling out what little hair I have last week when I was remotely setting up the DNS zone for my test SME zone in BIND and it was not working.  I was getting this weird message: "CNAME and other data".  Well, yes I was using CNAMEs, so?  Finally I grabbed one of the BIND authors and Rob mumbled under his breath on how one of his coders can't write error messages that don't read like EMAC messages...

Anyway, got ride of that CNAME for the zone; it has to be an A RR.  Which if I was home doing this I would have checked my Liu book and seen that.

Just some more BIND fun.

BTW, again, your packaging of DNS is great.  It is just the thing for those not dumb enough to do their own DNS server!      (I have been doing DNS servers off and on for 15 years, you would think I would remember....)

Correct. There is also no requirement that SME server is even aware of the hostname which is used in global DNS to identify it as MX for the domain. The MX hostname isn't used in the SMTP transaction.

Good, and thanks.  I am not familiar with QMail and could not discount things buried in config files that were set up at install time and not easy to change later.  SAMBA is like that; but that I know already.

[rgmhtt]

I don't see how your having a backup mail relay affects your choice of hostname. In any case, I'd advise you not to use a backup mail relay, as it reduces your ability to control spam without generating backscatter. Backup mail relays are unnecessary - sending hosts are required to spool the mail and attempt later redelivery.

The relay is to a FQDN, so if I change that (which I have a couple times over the years) I have to coordinate the change with my ISP.

My mailserver has a MX weight of 10.  My ISP's relays have weights of 25 and 35.  So mail only goes to them if I am off the net or totally swamped.

Over the years I have been off for over a day.  What with power outages and Telco accidents.  I am on mailing lists that have rather draconian rules and will drop you if you don't receive mail in 24 hours.  The mail relaying goes back before there was much spam.  I will check with my ISP.  I believe we are configured to prevent back scatter.

[CharlieBrady]

My mailserver has a MX weight of 10.  My ISP's relays have weights of 25 and 35.  So mail only goes to them if I am off the net or totally swamped.

Or if it is sent there by spammers.

I will check with my ISP.  I believe we are configured to prevent back scatter.

Unless your ISP can query in real time your valid user list, then they cannot prevent back scatter. If they can query in real time, then you don't need them because your server is on-line. QED.