Seriously, the iPhone is lacking one basic feature for email:

A simple button that allows us to "mark all messages as read"..

Could someone do a hack for that? Would be greatly appreciated!

Agreed, i was thinking about it today. We do need this!

Well someone has already created a SMS app which allows you to delete individual messages. It must be possible to create an app which marks all email messages as read.
Im willing to donate cash for this to happen.

After countless searches, I just broke down and went through each and every email, all 297 of them.

i have 4 mail accounts, pain in the ass

Looks like the Mail.app stores the information in a SQLite database. It shouldn't be too much trouble to interface to it, I'll take a look...

Ok! App done!
Get it here

A little basic for now, but seems to work well... I just have one mail account set up, so I didn't do much testing... Any problems, just say it!

thanks nop144666!
although basic it provides the functionality i require.
any chance of restarting the springboard when finished so that the mail icon updates correctly after deleting emails??

I was thinking more on the line of somehow updating the mail icon directly, but I guess restarting the springboard will do for now... Letzdoit

The Mail app is missing way more than just that.

POP folders for one, and storing e-mails locally for two.

Great utility BTW