Google blocking 7zip

[Ian Batten]

On 2 Apr 2014, at 08:57, Richard Hopkins <richard.hopkins at bristol.ac.uk> wrote:

> --On 28 March 2014 11:04 +0000 Richard Hopkins <Richard.Hopkins at bristol.ac.uk> wrote:
> 
>> However, *all* .7z (encrypted) archives are blocked, whether they contain
>> "dangerous" attachments or not.
>> 
>> I'm hoping that Google have made a mistake here which they will recognise
>> and fix real soon.
> 
> Which they appear to have. Encrypted .7z archives (so long as they don't contain "dangerous" attachments)

How do they tell what the contents are?  Does the 7z format allow the table of contents to be read without having the passphrase?

ian