The default setting for Gmail accounts on Apple iPhone and iPad devices is to archive messages rather than delete them when you swipe left. To correct this, follow these steps:
- Go to settings.
- Tap on Passwords & Accounts.
- Tap on the Gmail account to change.
- Tap on Account to expand out the options for the account.
- Tap on Advanced at the bottom.
- In the middle section of the Advanced options list you’ll find the “Move Discarded Messages Into” option. There is most likely a checkmark next to Archive Mailbox. Tap on Deleted Mailbox.
- Go back to Account.
- Tap Done.
Now when you swipe left for an email you’ll see Delete is an option.