spf-discuss
[Top] [All Lists]

Re: [spf-discuss] Does an SPF record need to be an IP?

2005-11-04 14:02:54
wayne schreef:

In theory, MX is cheaper than PTR because MX records get additional
processing.  The name servers send the A records for the domains
mentioned in the MX records along with the MX records.  PTR records do
not send the same info.  So, while MX record process may require the
same number of calls to the resolver, the actual number of DNS queries
that have to be sent over the internet is usually less because of
caching for MX lookups than for PTR.

This depends on the MTA you're using. At least one (Postfix) already
performs a reverse lookup for the client connecting to it and will also
check for a matching forward record. If your MTA happens to do this too,
the PTR mechanism is essentially for free (in terms of number of lookups
required), since the neccessary lookups have taken place already. This
usually will not be the case for the MX mechanism.

Regards,
Arjen

-------
Sender Policy Framework: http://spf.pobox.com/
Archives at http://archives.listbox.com/spf-discuss/current/
To unsubscribe, change your address, or temporarily deactivate your 
subscription, 
please go to 
http://v2.listbox.com/member/?listname=spf-discuss(_at_)v2(_dot_)listbox(_dot_)com