[imp] upload of large attachments failing

[Liam Hoekenga]

We have users who, against better judgement, want to send each other very large
files using email.  Our mail gateways will send messages upto 100MB in size. 
I'm trying to adjust IMP 4.x's settings to allow this.  I've changed the

    upload_max_filesize = 95MB

in my php.ini and I've changed

$conf['compose']['attach_size_limit'] = '99614720';

in imp/config/conf.php.  I'm trying to attach a file that's 80MB, and my browser
spins a bit and then says "Document contains no data".  My PHP error log says...

[Fri Jan 14 14:50:33 2005] [error] PHP Warning:  POST Content-Length of 84249891
bytes exceeds the limit of 8388608 bytes in Unknown on line 0

Where is it getting the 8388608 bytes setting?  We're using a SQL VFS backend
(MySQL), and vfs_data is a "LONGBLOB", so there should be plenty of storage
available (2^32, or 4GB, acc'd to the mysql docs).

Liam