Note Before: P.S: This method is relevant for Gmail and Google Apps e-mail accounts. Others like Yahoo Mail, Rediff only shows Delete and can’t be changed.
Most of the time when y read an e-mail in your Mail application of iPhone, iPad or iPod Touch), you move it out of your Gmail Inbox. You do it by swiping it. At this time this action showsyou an Archive Button which you select and Archive it. For me it was of not use as I don’t archive junks and notifications. I needed Delete option instead of Archive.This means we have to change default setting in iOS.
You have to change some settings. Open Settings on your Apple product and then navigate to Mails, Contacts, Calendars and at end select e-mail Account to make new change.Now you will see an option called “Archive Messages”. Swap it to OFF and you are done. Now, you will be able to send messages to Trash from Inbox etc.