On Dec 8, 2005, at 5:22 PM, Markus Stumpf wrote:
is anybody aware of MTA software that uses SRV records for mail
(in addition(?) to MX records)?
I don't know about the status of 2821bis - should they be mentioned?
Perhaps in respect to HELO/EHLO verification. : )
Should there be a precedence of SRV records over MX records? Should
MX records become obsolete?
While SRV records allow greater control over issues related to load
balancing, SRV has a problem related to how Microsoft uses these
records in their products. Unless this has changed over the last
year, Microsoft has a tendency to use long timeouts and appear to
hang when attempting to find servers that may be behind firewalls
pointed to by SRV records. This really means one must be careful
about what zones are public that contain SRV records. There is also
the issue that using a prefix precludes the use of a wildcard. As a
result of these two problems, I doubt that SRV will displace MX
MTAs would use
Is it useful (e.g. wrt 2821bis) to also have
There are some MTA software packages that are using an SRV record to
validate the EHLO and confirm that the MTA is authorized. The use of
this record simplifies dealing with the public zone issue and is
The related software can be found at: