If you use the Mail app on your iPhone to access one or more Gmail accounts, you may have discovered that, by default, you are unable to delete e-mails. Instead, e-mail is simply archived, removing it from your Inbox but leaving it in your Gmail’s “All Mail” folder. Fortunately, there is a way to change this, and it can be customized for each Gmail account. Prefer to have the ability to delete e-mails from your personal account but archive from your work account? Totally possible.
Step 1: Tap “Settings”
Step 2: Scroll down and tap “Mail, Contacts, Calendars”
Step 3: Tap the Gmail account you wish to change
Step 4: Tap the word “ON” next to “Archive Message.” This will switch it to OFF, which switches Archive to Delete