Step 1: Open Mail application on your iPhone device.
Step 2: Now click on the ‘Flagged’ Mailbox folder where all the flagged emails were stored.
Step 3: Choose the email or emails that you wish to unflag and clickn on ‘Edit’ button located at the upper right corner of your screen.
Step 4: If it prompts any confirmation pop-up, then proceed the same to un-flag the emails.
Step 5: Once you are done, the unflagged emails will display as normal as other emails under respective mail folders and those emails will not be available under ‘Flagged’ mail folder.