Remove ghost email from Mail autofill on Mac

From everything you have described, I do not think you are at the point where you need to delete Mail or rebuild your mailboxes.

The fact that the address appears only on your iMac, is not associated with any current mail account, is not in Contacts or Previous Recipients, and does not appear on your iPhone strongly suggests that it is being stored somewhere locally on the Mac rather than coming from an email provider.

The first place I would look is in Mail's settings. Open Mail > Settings > Accounts and examine each account carefully, even the ones you actively use.

Look for any secondary email addresses, aliases, or sender identities that may have been saved years ago. Then check Mail > Settings > Composing to see what is selected for "Send new messages from."

It is also worth opening System Settings > Internet Accounts to make sure there is not an old Google, Exchange, Yahoo, or other account that remains on the Mac in a disabled state. Sometimes these can leave behind sender identities even after they are no longer being used.

If everything looks correct there, the next possibility is that Mail has retained the address in its local preference files.

In that case, quit Mail and make a backup of the file named com.apple.mail.plist in your ~/Library/Preferences folder by moving it to your Desktop.

When Mail is opened again, it will create a fresh preferences file. This resets Mail's preferences but does not delete your messages, and it is often enough to remove an old sender identity that has become stuck.

Another useful clue is how the address appears. If it is always listed in the From: menu before you type anything, then it is almost certainly stored as a sender identity.

If it only appears after you begin typing, then it is more likely to be an autocomplete entry, even if it is not showing up in Previous Recipients.

Before suggesting anything more drastic, I have a couple of questions that would help narrow this down.

When you click the From: pop-up menu in a new message, does the ghost address appear immediately in the list, or does it only appear after you start typing?

Also, does the address appear by itself, or is it shown with a display name, such as Layout <Layout@...org>? Those details will help determine exactly where Mail is getting it from.

It sounds like you are dealing with a “ghost” sender identity in Apple Mail rather than a real Mail account.

The details you provided are very helpful because they rule out the usual places where an account would exist.

Since Layout@XXXXCC.org does not appear in Mail > Settings > Accounts, does not appear in System Settings > Internet Accounts, and remained after removing com.apple.mail.plist, Mail is most likely remembering it as a stored sender identity rather than an actual account.

The fact that it appears only as Layout@XXXXCC.org with no name attached is another clue that it is probably a cached address or leftover account identity.

The first thing I would check is Mail’s Previous Recipients list.

Open Mail and go to Window > Previous Recipients. Search for Layout or the domain name.

If you see that address there, select it and remove it.

Then quit and reopen Mail to see whether it disappears from the “Send new messages from” menu.

If it is not there, the next place to look is Mail’s internal data.

Quit Mail completely.

In Finder, hold the Option key while opening the Go menu, choose Library, then open the Mail folder.

Inside, you should see a folder beginning with something like V10, V11, or V12 depending on your macOS version.

Inside that folder, open the MailData folder and search the files there for Layout@ or XXXXCC.org.

If you find that address, it should reveal where Mail is storing the leftover identity.

Another place worth checking is Keychain Access. Open Applications > Utilities > Keychain Access and search for Layoutand the domain name.

If there is a Mail-related entry for that address, it may be contributing to the sender list.

One thing I would like to confirm before suggesting the exact file to remove is your macOS version.

Are you using Ventura (13), Sonoma (14), Sequoia (15), or another version?

Apple changed the Mail storage structure between versions, so the cleanest removal method depends on that.

Check again

The usage of “layout@ “ was used ONLY AS AN EXAMPLE

Substute the name of the Offending email address - that is a no brainer

Good Work there 👍