Properly sort Drafts, Deleted, and Sent mail on the iPhone
Assuming that you have followed the iPhone IMAP setup instructions, it is now time to properly configure your mobile Mail client so that Sent Mail, Deleted Mail, Drafts, and Junk are reflected properly after syncing back between the webmail client and any other desktop clients you may have.
1. Open ‘Settings’ > ‘Mail’ > [Your Gmail IMAP account] > ‘Advanced’
2. Select ‘Drafts Mailbox’ > ‘On the Server’ > ‘[Gmail] Drafts’. Return to the ‘Advanced’ view.
3. Select ‘Sent Mailbox’ > ‘On the Server’ > ‘[Gmail] Sent Mail’. Return to the ‘Advanced’ view.
4. Select ‘Deleted Mailbox’ > ‘On the Server’ > ‘[Gmail] Trash’. Return to the ‘Advanced’ view.
Any emails sent from your iPhone will appear in Gmail’s ‘Sent’ view, any saved drafts saved on your iPhone will appear in Gmail’s ‘Drafts’ view, and any deleted messages will be reflected in Gmail’s ‘Trash’ view.
via How-to: Proper Gmail IMAP for iPhone & Apple Mail – Derek Punsalan – 5ThirtyOne.
So I was having an issue on my iPhone where my Gmail wasn’t syncing properly.