Comment 8 for bug 643223

With help from Haw I tested this on qastaging:

 * mail From my gmail address: accepted
 * mail From my canonical address, via gmail, signed by gmail: accepted (the point of this bug)
 * unsigned mail attempting to create a new bug: rejected
 * gpg signed attempting to create a new bug: accepted
 * unsigned mail appending to an existing bug (weak auth ok): also accepted

so it looks all ok.

There is a follow-on <https://code.launchpad.net/~mbp/launchpad/mail-script/+merge/75488> but it only affects developer tools and doesn't need qa.