(a) It seems that there must exist a folder for archiving emails so that archiving emails can work. The following steps will set the folder for archiving emails: "Settings" > "General settings" > "Accounts" section > tap the account you want to configure > "Folders" > "Archive folder" > select a folder (usually "Archive" folder). Do not select "None" or "Automatic (None)". (b) Methods to archive an email: Method 1: (In the email list) select the email by long-pressing it or by tapping the icon before the email > tap the "Archive" icon above the email list. Method 2: (Inside the email) tap the "Archive" icon above the email. If you do not see "Archive" icon above the email, the following steps might be helpful: "Settings" > "General settings" > "Display" > "Visible message actions" > tick "Archive" > "OK". Method 3: (Inside the email) tap the vertical three dots on the upper right corner > "Refile..." > "Archive". Method 4: 4.1. You can configure swipe actions to "Archive": "Settings" > "General settings" > "Interaction" > "Swipe actions" > configure action for "Right swipe" or "Left swipe" to "Archive". 4.2. Then you can right-swipe or left-swipe the email to archive it.