Internet mail fails to some domains

Internet mail fails to some domains

Post 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

 
 
 

Internet mail fails to some domains

Post 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



 
 
 

Internet mail fails to some domains

Post 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


 
 
 

Internet mail fails to some domains

Post 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


 
 
 

1. Internet mail fails to some domains

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

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