IPhone :: Select All Mail At A Time?

I have so many mails a day and I'd like to read and delete them selectively. News letters from shopping mall sites, business mails from partners, customer's feedback mails and notification mails from SNS ..... After reading some interesting mail, there's mails I don't want to open for today. I mean it's NOT that I stop subscription, just wanna delete for now. But, there's no "Select all" button in Mail List and I cannot select mails to be removed all at a time. So, the Mail app force me to tap each mails that I don't need to touch (one at a time... one at a time) Given that you've got mails too lot a day, the number of times you have to tap would really mass up your day life! To delete all, We should go to trash box and tap 'delete all'but before we move each mail we need select all button. it's deferent delete all and select all. delete all button is enough and useful for now in trash box. I think select all button in Mail Inbox(List) is urgent issue.

Info:
iPad 2 Wi-Fi + 3G, iOS 5.1