Restrict SMTPSVC to UDP DNS under W2K Pro

[Andrew Aronoff]

I would like to configure the SMTPSVC to use UDP for DNS queries. A
method is explained in MSKB 330070, "Mail May Not Be Delivered When
DNS Resolution Uses Only the UDP Protocol".

According to that article, UDP can be configured with MetaEdit by
adding the name "36997" with a value of 2 (DWORD) at the location
LM\SmtpSvc\1

However, under W2K Pro SP4, this does not appear to have any effect.
"NETSTAT -n" shows that DNS queries still proceed via TCP, not UDP.

Is there any way to restrict SMTPSVC DNS queries to UDP under Windows
2000 Professional (SP4)?

regards, Andy

P.S.: This was posted to microsoft.public.inetserver.iis.smtp_nntp:
http://tinyurl.com/ceoxe ... but it received no response.
--
**********

Please send e-mail to: usenet (dot) post (at) aaronoff (dot) com

To identify everything that starts up with Windows, download
"Silent Runners.vbs" at www.silentrunners.org

**********

 

[Kevin D. Goodknecht Sr. [MVP]]

I would like to configure the SMTPSVC to use UDP for DNS queries. A
method is explained in MSKB 330070, "Mail May Not Be Delivered When
DNS Resolution Uses Only the UDP Protocol".

According to that article, UDP can be configured with MetaEdit by
adding the name "36997" with a value of 2 (DWORD) at the location
LM\SmtpSvc\1

However, under W2K Pro SP4, this does not appear to have any effect.
"NETSTAT -n" shows that DNS queries still proceed via TCP, not UDP.

Is there any way to restrict SMTPSVC DNS queries to UDP under Windows
2000 Professional (SP4)?

regards, Andy

P.S.: This was posted to microsoft.public.inetserver.iis.smtp_nntp:
http://tinyurl.com/ceoxe ... but it received no response.

This is because many MX queries won't resolve using UDP, the MX records
won't fit into one packet and will be truncated. A truncated DNS record
lookup will fail.
The is why Win2k3 DNS supports EDNS which allows UDP packets over 512 bytes.
This allows the DNS server to return the record on the first query using
UDP. If the records won't fit into one UDP packet, the client will query
again using TCP.

 

[Andrew Aronoff]

Thanks, Kevin, for your response.

... many MX queries won't resolve using UDP, the MX records
won't fit into one packet and will be truncated. A truncated DNS record
lookup will fail.

Some MX queries that use UDP will fail. However, most will succeed. Is
there any way to configure the SMTPSVC under W2K Pro (SP4) so that
it's restricted to UDP per MSKB 330070?

The is why Win2k3 DNS supports EDNS

EDNS would most likely not be supported by my router, whose proxy DNS
only accepts UDP queries. Also, W2K3S is not appropriate for my needs
or my budget.

regards, Andy
--
**********

Please send e-mail to: usenet (dot) post (at) aaronoff (dot) com

To identify everything that starts up with Windows, download
"Silent Runners.vbs" at www.silentrunners.org

**********