If you send an email to an invalid email address, that address will ‘stick’ in Outlook via the AutoComplete list. Here’s how to fix that.
Let’s say you send an email to [email protected] (misplaced period/fullstop). The email will ‘bounce’ with an error message. Despite that, the wrong email address still appears in the AutoComplete list.
If you’re not careful, you’ll make the same mistake again by choosing from the AutoComplete list.
To fix that, you need to manually delete the incorrect entry. Look for the black X on the right side of the list – click on it to remove the entry. Or press the DEL (Delete) key when an AutoComplete entry is selected.
In earlier versions of Outlook (like Outlook 2007) there was no black X but the DEL key trick works.
Microsoft added the black X to give people the ‘hint’ that editing the AutoComplete list was possible.
Changed email address
It’s a similar problem if someone changes their email address. You update your Contacts list and you have to delete the old address from AutoComplete.
See AutoComplete in Outlook – Complete for more details.
We tested this in late April 2017 with Outlook 2016 for Windows version 1705. A pleasant surprise! Outlook appears to ‘read’ the bounce email from an invalid address and delete the incorrect email address from the AutoComplete list. (ie the invalid address is added to the AutoComplete list but is removed after the bounce message arrives at the Inbox).
This isn’t documented anywhere we can find, so it’s unclear when this feature was added.
It only applies to badly formatted email addresses (like the @fred.daggcom example above). Properly formatted but incorrect addresses (ie a deleted mailbox) still stick in the AutoComplete list.