Should I worry about NULLs in 7-bit?

Hello,
I am currently writing the first ever (I think) gateway between
X.400 and MIME that follows the MIME-MHS specifications.

Now I have a nit to worry me:

- RFC 822 and MIME do not outlaw the NULL character inside quoted strings
  of the heading.
- RFC 822 and MIME do not outlaw the NULL character inside the body in
  7-bit encoding.

The code will have more lines if I worry about this than if I don't.
(Of course, the code will handle the cases of NULLs inside Q-P or Base64
encoding!)

So, opinions are sought:

- It is CRITICAL to allow NULLs inside headings and text
- It is nice to have, but an initial version that ignores it is OK
- It is a bug in the specification, and nobody cares about it

How are these opinions distributed across the Net.Gurus?
Regards,

                      Harald Tveit Alvestrand
                      Implementor (!)