RFC 2821, "Simple Mail Transfer Protocol", April 2001
Note: This RFC has been obsoleted by RFC 5321Source of RFC: drums (app)
See Also: RFC 2821w/ inline errata
Errata ID: 377
Publication Format(s) : TEXT
Reported By: Richard O. Hammer
Date Reported: 2002-10-17
Section 5 says:
Two types of information is used to rank the host addresses: multiple MX records, and multihomed hosts.
It should say:
Two types of information are used to rank the host addresses: multiple MX records, and multihomed hosts.
The verb in that sentence should be "are" not "is".