Archiving a message in Gmail conveniently hides it from the Inbox while a copy is kept in All Mail and other labels for search and reference. Archive an email you sent as much as you like, though, and it still won't disappear from Sent Mail… until you delete it — which means it's gone from All Mail and all labels, too.
Fortunately, the web interface is not the only way to access Gmail, and IMAP lets you strip any email you sent of the Sent Mail label while keeping an archived copy in All Mail.
Delete an Email from Gmail "Sent Mail" But Keep an Archived Copy in "All Mail"
To remove an email you sent from Gmail's Sent Mail folder while still keeping a copy under All Mail:
- Set up Gmail access in a desktop or mobile email program using IMAP.
- Find the message (or messages) you want to remove in the [Gmail]/Sent Mail folder.
- If you mapped that folder to your email program's standard folder for sent items, look there, of course.
- Move the messages to the [Gmail]/All Mail.
If you delete the message in the Gmail web interface under Sent Mail, it will be moved to the Trash and eventually will disappear completely, even if you have archived it before.