Instant Search can be used to find flagged items within the selected folder or across all mail folders. On the Home tab, in the Find group, click Filter E-mail, and then click Flagged.
Go to Settings > Mail, then tap Accounts. Do one of the following: If you're using an iCloud email account: Tap iCloud, tap iCloud again, then tap iCloud Mail. If you're using another email account: Tap your email provider, then tap your email account.
With the Mail app open, shake your phone back and forth. 2. A box titled "Undo Trash" will appear. Tap "Undo." The email should reappear in your inbox.
Recover a deleted email
In the Mail app , you can delete or archive emails you no longer need. If you change your mind, you can recover deleted emails.
Recover>
Tap Trash.
When an email message is archived in Gmail, it simply means that an “Archive” label has been attached to it. So, to retrieve an archived email, you need to locate the message and remove the “Archive” label. Once you've located your archived email, open it and go to the “Move” icon in the toolbar.
To recover an email from the Outlook App:
Go to the home screen and tap the home button and the search feature pops up. Type keywords in the search field at the top to find old emails there as well. When you tap on that email in the search, the mail app will open and you can read the email.
How to Retrieve Mail from a Previously Inactive Email on iPhone
To retrieve the archived message, open the email and tap on the three dots at the top right of the screen. Tap “Move to inbox”, and your message will be instantly sent back to your inbox and the “Archive” label removed.
How to retrieve archived emails in Gmail
How to find archived emails in Gmail on Android?
Type CTRL+Z for “undo”. Check your drafts folder. Restart your email program or browser and check the drafts folder again.
The best thing that you can do is to use the provider to find the old email account or old messages. All of the major providers, including Outlook, Gmail, Yahoo, and AOL, have recovery tools available. If the email address is from a lesser player in the email game, again, you might be out of luck.