Re(2): The subject line leakage problem

[Jim Craigie <Jim.Craigie@xxxxxxxxxxxxxx>]

> Now, in theory X.400 MTAs only deal with the envelope and are able to pass
> arbitrary content types around, making it possible to introduce new ones at any
> time. Howevr, I've found that sometimes this works in practice and often it
> doesn't. Support for this in real world X.400 implementations is far from
> uniform. At least part of the reason why this is so is because this capability
> is rarely used, and rarely used capabilities are bound to have bugs, especially
> given that most X.400 implementations are rarely updated these days.

I don't know what X.400 systems you are basing the above comment on. I've been involved with interoperability testing STANAG 4406 PCT (just CMS really), and we have not seen a single problem with an X.400 MTA being unable to relay the new content type. 

> There are, however, things you can do in SMTP. One of them is to secure
> a batch SMTP session (RFC 2442). There are a number of email systems
> that support this approach. I suppose something similar is possible in 
> X.400 (a P1 content type?), but AFAIK nobody has ever defined such a 
> thing.

The X.400 standard defines a double-envelope content-type precisely to allow protection of the envelope where required.

Jim