Haha, good catch. I was just testing different things in that file. I have removed the validators in mail_user.tform.php. And I tried to set it to a double. As a double it prevents the overflow. But we need to be able to have a FLOAT. But there isn't that option. It needs to be added....
I found the problem that overflows the INT. it's in the tform.inc.php file, but it's line 517. If you remove the intval there then the record won't overflow. It'll just be capped at just shy of the max. I'm going to submit this patch to prevent the overflow.
Another bug bites the dust. So, the current issue with the mail module is that the quota is capped at a max of 2GB per account. This can't be fixed until tforms.inc.php has the feature for FLOAT added to it.
But a float does not mean that its a integer or bigint, so to test if its a float is not sufficient here in my opinion.
