Question regarding symbols in name resolution

mark Mullai mmullai at yahoo.com
Thu Apr 19 23:59:21 UTC 2001


 Hey I have an email ID for years m_mullai at hotmail.com never had any difficulties.

Mark


  Jim Reid <jim at rfc1035.com> wrote: 
>>>>> "Patrick" == Patrick McAllister writes:

Patrick> As I understand it, certain symbols are "forbidden" in
Patrick> DNS, one of which is the underscore. 

You are mistaken. The DNS protocol imposes no restrictions on the
character set that may be used for names. The only limits are the
length of a label and the overall name. See RFC1035. Some applications
that use the DNS may impose their own restrictions. For instance
RFC1123 defines what's allowed in a host name and RFC822 says what can
be used for an email address. BIND8 enforces the 1123 standard on the
names of A records, which means they can't by default contain
underscores. These checks can be over-ridden. They are not enforced by
BIND9.

Patrick> My problem is this,
Patrick> I have a client who has a mail server they have named
Patrick> companyxyz_smtp at xyz.com. They actually seem to get mail
Patrick> fine from everyone except one organization. This one
Patrick> organization, say company abc, claims they cannot send
Patrick> mail to company_xyz because of the underscore.

This has nothing whatsoever to do with the DNS. Mail systems lookup
what's on the RHS of the @ sign in the DNS. What's on the left hand
side only matters when local delivery is attempted. The DNS never sees
things like " companyxyz_smtp".

Patrick> Is an underscore indeed a "forbidden" character? If so
Patrick> how is it no one except company abc seems to be having
Patrick> these issues.

It is not a "forbidden" character in a mailbox name. Get this company
to read RFC822 and make their mail system comply with that standard.



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