What are the character restrictions on boundaries in an email?

For instance, the following seems to cause GW to choke:


And on the surface, I would think that a "/" is invalid. But I seem to see
quite a few of them, especially on bounce messages (I'm sorry to inform you,
but your email to such-and-such was too big.)

Perhaps could we get GW to handle exceptions like this instead of choke and
spit them out as a bad message? Changing the boundary fixes the email . .