Talk:MX record
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Regarding the priority of selecting mail servers, I am unclear what "the shortest distance" refers to. But, according to http://www.han.com/dns.html, the mail server with the lowest priority number is selected first.
- "Distance" is Dan Bernstein's word for what the IETF calls "Priority". I've updated the article to clarify. — mendel ☎ 00:49, Jun 16, 2005 (UTC)
Suggestion from little old me: maybe list the standard default locations for MX Records. I viewed this article in an attempt to figure out where Apache hides the MX records.
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the external link: "MX Record Lookup" appears to be an email harvesting site. It insists on a full email addy (not just a domain) before providing an MX record lookup.
Which link are you referring to? I tested them all and I could not find one that insisted in getting a full email address.
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I don't know how accurate the info is, but I was trying to find the maximum priority value... the only reference I could find was http://www.petri.co.il/configure_mx_records_for_incoming_smtp_email_traffic.htm and this said it's 0 to 65535 (so I guess 2 bytes unsigned)... think it's worth adding to the page but would like a more solid reference (like an RFC document).
[edit] IN A versus IN CNAME
Hello, I'm wondering if there should be some explanation about the use of a hostname in the MX record that is defined as an IN A host or a IN CNAME host.
Picture the following scenario:
mx1 IN A 192.168.1.1 mail IN CNAME mx1 acme.com. IN MX 10 mail.acme.com.
the host mx1 would receive email for the acme.com domain, it would then look at the list of MX records to determine if it should forward it to another exchanger or try to deliver it locally. Since mx1.acme.com != mail.acme.com, it may try to contact mail.acme.com (itself) to forward the mail causing an SMTP 554 - local configuration error message.
Most new SMTP servers handle this situation gracefully, but I wonder if this information should be listed in the entry for MX record.
RFC 1912 strongly discourages an MX pointing to a CNAME by referencing RFC 1034 and RFC 974. This is also staed in RFC 2181 Section 10.3 By corollary, NS and SOA records should not point to a CNAME (especially since as of version 9, Bind will not query for the glue record from a root nameserver for the additional section by default). -Cowbert 22:13, 8 September 2006 (UTC)
[edit] equal weight MX records
"If there is more than one entry with the same preference number, all of those must be tried before moving on to lower-priority entries."
Is there any references for this? A number of systems seem to try just one server at random of equal perference and then give up. The RFC 2821 is not explicit: If there are multiple destinations with the same preference
and there is no clear reason to favor one (e.g., by recognition of an easily-reached address), then the sender-SMTP MUST randomize them to spread the load across multiple mail exchangers for a specific organization.
