Is there a maximum support subject length?

We have noticed that any emails with a subject length greater than 100 characters send ok, but the 'sent email' record is not created and the 'email send' record always reports 0 messages, 0 deliveries etc, even though the email has gone ok.

Is this a bug?  Or is it by design that email subjects should not be more than 100 characters?  Which seems a bit below generally accepted limit of perhaps 255.

Also, perhaps if this is an agreed limit, it should raise a warning or error to indicate, rather than just not tracking correctly.

Thanks

Davinder