This is problematic for those with big inboxes since it would be very frustrating to manually select multiple mails in order to perform an action.
We have a new jailbreak tweak fix for you. AllMail is a Cydia tweak which appears in the upper right corner of the Mail app when you hit the Edit button and offering a number of options including Select All, Delete All, Move All, Mark All, and Hide All. This tweak as you must have noticed can completely kick Delete Mail or Mark Read out of the picture.
The initial release for this tweak contained a few bugs, but an update was released to fix these bugs.
AllMail is available on Cydia store for $1.50.