Questions I hear asked often are “What is the Archive folder (or All Mail) folder and what am I supposed to do with it? And why does an Archive button appear on my iPhone instead of Trash?”
The answer, well, depends, on whether you’re using Google Mail/Gmail, or every other mail system.
Non-Google mail hosts:
If you’re using iCloud, Exchange, Outlook.com, AOL, Yahoo, or any other non-Google mail provider, the Archive folder is just an ordinary folder that has been designated for “messages I don’t want in my Inbox any more, but I also don’t want to trash.” For those who already make their own mail folders for saving mail, this might not serve much purpose, and you probably wish to ignore it. For those who don’t file their saved mail, Archive gets messages out of sight while still holding on to them.
Google Mail (including Gmail):
Gmail does things its own way, and the Archive concept behaves differently that of that other systems. In Gmail, all mail, whether it’s in your Inbox, Sent, or another folder, appears in a folder called, well, All Mail. If you remove something from All Mail, you delete it from everywhere else it might appear in Gmail.
To Gmail, the concept of “Archive” means “remove from inbox.” In other words, the message will remain in All Mail—it was always there in the first place—but mixed in with every other message you have, including Sent and other items still in your Inbox. There is no designated place for “archived mail” that is separated out from your Sent Mail or current Inbox; if that’s what you want, make a folder for it, and don’t use the Archive button in Apple Mail.
Archive button in Mac Mail:
In Mac Mail, if you want an Archive button in addition to the Delete and Junk buttons in your toolbar, go to the View menu and choose Customize Toolbar, then drag the Archive button into your toolbar. If you want to remove it, drag it off your toolbar.
Trash can or Archive box on iPhone/iPad?
On iPhone or iPad mail, you can control whether or not you see a default Trash icon or an Archive icon in your mail, by going to Settings > Mail > Accounts > (the mail account) > Account > Advanced > Move Discarded Messages Into: > (one page back in upper left) > Done. Regardless of which is your default, you can always choose either one on a per-message basis by holding your finger down on it, which will pop up a menu.
Most mail systems will default to a Trash can when you add an account, but Google/Gmail accounts default to Archive. If you want Trash instead, change it after you add the account.
You can also control the appearance of Trash and Archive buttons when swiping left or right in the message list under Settings > Mail > Swipe Options.