Multiple SOA records?

[Lars Hecking]

 RFC 1935 says:

    2. Exactly one SOA RR should be present at the top of the zone.

 Note: "should", not "must".

 What kind of consequences can I expect trying to resolve records in a
 domain that has more than one SOA? The domain that is making problems
 is traininghott.com. Querying for its SOAs returns SERVFAIL, but querying
 the domain's name servers directly returns two (different) SOAs. This
 appears to create problems with mail (not sure here - another entity in
 my organisation is experiencing the problem).