On 2010-02-15 02:06, dar...@chaosreigns.com wrote:
Thank you for contacting us. An underscore is only legal for specific
types of DNS records, such as 'SRV'. 'A' records should only contain
letters, numbers and dashes. You may want to consider using '-' as
a substitute. I hope this helps. Please don't hesitate to contact us
should you have any further questions or concerns.
I'm finding *nothing* else that uses underscores in the names of A records.
I'm thinking I should stick with "mtx" instead of "_mtx".
Please let me know if there is some evidence I'm missing that it's
reasonable to use an underscore in this context.
The point of using an underscore in "special" records is that the "host"
is *not* a normal hostname.
DKIM (including ADSP) uses _domainkey.domain.example:
http://dkim.org/specs/rfc4871-dkimbase.html#rfc.section.7.4
http://www.rfc-editor.org/rfc/rfc5617.txt
According to the DKIM and OpenSPF folks (and, less important,
WikiPedia), underscore is forbidden in hostnames only:
http://domainkeys.sourceforge.net/underscore.html
http://www.openspf.org/DNS/Underscore
http://en.wikipedia.org/wiki/Hostname#Restrictions_on_valid_host_names
I could use TXT records. I kind of like the A records. Well established
for DNS BLs and WLs and all.
TXT records might be, prinicpally, the "correct" way to do this, but A
records are more efficcient and some caching only DNS proxies might be
set up to cache A record lookups (negative and positive) better than TXT
records.
If there is to be a policy record, maybe that should be a TXT record,
but I too like the A record for the actual MTX lookup.
Regards
/Jonas
--
Jonas Eckerman
Fruktträdet & Förbundet Sveriges Dövblinda
http://www.fsdb.org/
http://www.frukt.org/
http://whatever.frukt.org/
