Very Computer

by **Andrew Savene** » Sun, 11 Mar 2001 01:20:14

I am having a problem sending Internet E-mail from an Exchange 2000 server
to certain Internet domains. I have traced the problem to an issue with DNS
and MX records: If the MX record points to a CNAME record then mail will
fail (the log states that the host could not be contacted), whereas if the
MX record points to an A record the mail goes through successfully.

I found article Q153001
<http://support.microsoft.com/support/kb/articles/Q153/0/01.asp?LN=EN-...
gn&FR=0&qry=name%20records&rnk=6&src=DHCS_MSPSS_gn_SRCH&SPR=EXCH2K> which
states that, "RFC 1123 explicitly states that SMTP mail should be addressed
to canonical name hosts. To be canonical, the DNS entry must be an A record
or an MX record. CNAME records are not canonical and should not be mixed
with MX records."

This is fine, but Exchange 5.5 was able to handle this; does anyone know of
a fix for Exchange 2000?

Thanks,

Andy Savener
CCNA, MCSE+I

by **Judy Mendoz** » Mon, 19 Mar 2001 00:55:53

Andrew,

Did you find a resolution? I have the same problem with certain domains not
excepting e-mail.

These domains all worked with Exchange 5.5.

Regards,

Judy Mendoza

Quote:> I am having a problem sending Internet E-mail from an Exchange 2000 server
> to certain Internet domains. I have traced the problem to an issue with
DNS
> and MX records: If the MX record points to a CNAME record then mail will
> fail (the log states that the host could not be contacted), whereas if the
> MX record points to an A record the mail goes through successfully.

> I found article Q153001

<http://support.microsoft.com/support/kb/articles/Q153/0/01.asp?LN=EN-...

> gn&FR=0&qry=name%20records&rnk=6&src=DHCS_MSPSS_gn_SRCH&SPR=EXCH2K> which
> states that, "RFC 1123 explicitly states that SMTP mail should be
addressed
> to canonical name hosts. To be canonical, the DNS entry must be an A
record
> or an MX record. CNAME records are not canonical and should not be mixed
> with MX records."

> This is fine, but Exchange 5.5 was able to handle this; does anyone know
of
> a fix for Exchange 2000?

> Thanks,

> Andy Savener
> CCNA, MCSE+I

by **Chri** » Thu, 22 Mar 2001 10:01:18

What kind of connection are you using to access the internet? I had the same
problem and found that certain domains don't accept messages from a dial-up
connection. Try routing to someplace like mail.earthlink.net for the mail
going to
those domains.

Chris

> Andrew,

> Did you find a resolution? I have the same problem with certain domains
not
> excepting e-mail.

> These domains all worked with Exchange 5.5.

> Regards,

> Judy Mendoza

> > I am having a problem sending Internet E-mail from an Exchange 2000
server
> > to certain Internet domains. I have traced the problem to an issue with
> DNS
> > and MX records: If the MX record points to a CNAME record then mail
will
> > fail (the log states that the host could not be contacted), whereas if
the
> > MX record points to an A record the mail goes through successfully.

> > I found article Q153001

<http://support.microsoft.com/support/kb/articles/Q153/0/01.asp?LN=EN-...

- Show quoted text -

> > gn&FR=0&qry=name%20records&rnk=6&src=DHCS_MSPSS_gn_SRCH&SPR=EXCH2K>
which
> > states that, "RFC 1123 explicitly states that SMTP mail should be
> addressed
> > to canonical name hosts. To be canonical, the DNS entry must be an A
> record
> > or an MX record. CNAME records are not canonical and should not be mixed
> > with MX records."

> > This is fine, but Exchange 5.5 was able to handle this; does anyone know
> of
> > a fix for Exchange 2000?

> > Thanks,

> > Andy Savener
> > CCNA, MCSE+I

by **Bill Kearne** » Sat, 28 Apr 2001 15:10:23

Technically, it's the receiving hosts that need fixing. The RFCs clearly
state an MX record MUST NOT point to a CNAME. The fact that 5.5 did it
"wrong" doesn't mean 2000 should continue to support the incorrect behavior.

A possible alternative is to use something else as a smart host and route the
Exchange mail through it. If the domains are known (and few) it's possible to
route them within Exchange (still using a smart host).

> Andrew,

> Did you find a resolution? I have the same problem with certain domains not
> excepting e-mail.

> These domains all worked with Exchange 5.5.

> Regards,

> Judy Mendoza

> > I am having a problem sending Internet E-mail from an Exchange 2000 server
> > to certain Internet domains. I have traced the problem to an issue with
> DNS
> > and MX records: If the MX record points to a CNAME record then mail will
> > fail (the log states that the host could not be contacted), whereas if the
> > MX record points to an A record the mail goes through successfully.

> > I found article Q153001

> <http://support.microsoft.com/support/kb/articles/Q153/0/01.asp?LN=EN-...
> > gn&FR=0&qry=name%20records&rnk=6&src=DHCS_MSPSS_gn_SRCH&SPR=EXCH2K> which
> > states that, "RFC 1123 explicitly states that SMTP mail should be
> addressed
> > to canonical name hosts. To be canonical, the DNS entry must be an A
> record
> > or an MX record. CNAME records are not canonical and should not be mixed
> > with MX records."

> > This is fine, but Exchange 5.5 was able to handle this; does anyone know
> of
> > a fix for Exchange 2000?

> > Thanks,

> > Andy Savener
> > CCNA, MCSE+I

Very Computer

Internet mail fails to some domains

Internet mail fails to some domains

Internet mail fails to some domains

Internet mail fails to some domains

Internet mail fails to some domains