Q: What is the bottom centre icon when viewing an open email iphone 5

Uncadon,

The one that looks like a trash can?

If it's a Gmail account then you may have Archiving switched on.  This means the messages are being archived rather than going into trash.  If you go to Settings and into Mail, and then to the settings for the email account, you can turn archiving off.  The middle icon will then be a Dustbin ("Trashcan" if you must! ), and messages will then go into your trash folder.

Uncadon,

Sounds like a Gmail archive icon. "When you archive a message, it moves to the All Mail folder. It does not delete it from the Gmail account. Archive replaces all delete options when using a Gmail account, including using the Trash icon while viewing a message and selecting Edit to manage multiple messages. You can disable this feature in Settings > Mail, Contacts, Calendars > Gmail Account > Archive Messages:"

You are welcome.

Thanks for to tip , now the question is how to get to archived emails.   When disabling the archive function, would the emails go back to the inbox ?