For years, Outlook users had a simple safety net against sending email to the wrong person. If a stale, mistyped or outdated address appeared in the suggestions under To, Cc or Bcc, many users could click the small “X” beside it and stop that suggestion appearing again. But following Microsoft’s 31 March 2026 retirement of “Contact Masking”, and recent changes to how Outlook generates recipient suggestions, that familiar control is no longer behaving consistently across Outlook clients. Microsoft says the AutoComplete list is not affected. Many users say the experience tells a different story.
Contact Masking was one of the features users experienced through that familiar “X”. It allowed a user to hide a specific suggested recipient, so that the address would no longer appear when they composed a new message. Microsoft says it had become a recurring source of customer confusion and support escalations, because contacts could be hidden for one user but remain visible to others, and the behaviour was inconsistent across Outlook, Teams and Microsoft 365 Search. In its retirement notice (MC1234566), Microsoft says no replacement is planned for Contact Masking, and that previously hidden contacts may now reappear in addressing fields.
On paper, that should not affect the separate AutoComplete list, the locally cached suggestions Outlook builds up from addresses you have sent to before. In its own retirement notice, Microsoft is at pains to say that the AutoComplete list for Outlook will not be impacted by this change, and that users can still remove entries from their autocomplete history. Microsoft’s published guidance on the AutoComplete list still tells users they can remove an individual entry by selecting the X beside a name, or by highlighting it and pressing Delete. In theory, the X for Contact Masking is gone, but the X for AutoComplete should remain.
In practice, reports on Microsoft’s own Q&A forum and from the long-standing Outlook specialist site Slipstick describe a different experience. Users say the X to delete individual autocomplete entries has disappeared in recent Classic Outlook builds — Version 2604, Build 19929.20086 has been specifically cited — and that individual entry deletion is no longer reliably supported in the New Outlook for Windows either. Entries that appear to be removed sometimes reappear. Whether this is an unintended side-effect of the Contact Masking retirement, a separate regression that has landed at the same time, or a consequence of how Outlook now generates suggestions in Exchange Online environments, the practical effect on users is identical: the small UI control they relied on to clean up bad suggestions is no longer doing its job.
That last point is worth unpacking. Microsoft has been gradually shifting how Outlook decides who to suggest. From Outlook for Microsoft 365 Version 2202 (Build 14931.20604), the To, Cc and Bcc compose suggestions for mailboxes connected to Exchange Online are powered by Microsoft Search rather than the traditional, locally stored AutoComplete cache. Microsoft’s own support page notes that, in this configuration, some older AutoComplete guidance no longer applies. That blurs the line between contacts, autocomplete entries, and search-powered suggestions, and it is one reason the documentation in this area has become harder to follow than it once was.
For SMEs, this is not a cosmetic issue. Autocomplete suggestions are one of the most common causes of misdirected email. An old supplier address, a former member of staff, an ex-client, or a similarly named contact sitting in the suggestions list is a real data-protection risk every time a user starts typing in the To field. The UK Information Commissioner’s Office, in its data-protection guidance for small organisations, explicitly lists sending emails to the wrong recipient as a common mistake and recommends considering turning off the Autofill tool when sending work emails. For many users, the correction appeared to be a single click. The current alternatives are noticeably heavier: clear the entire autocomplete list and lose every learned suggestion, delete or correct the underlying contact in the People or Contacts area, or in some clients turn off Suggested people entirely, which clears the list and starts fresh once re-enabled. None of these is a like-for-like replacement for being able to remove one bad entry.
For organisations affected, the short-term reality is that users should be reminded to slow down on the To line, especially when sending sensitive information or replying to long-running threads where an old address may still be lurking. Helpdesk teams should expect a rise in “Outlook keeps suggesting the wrong address” tickets, and should update internal guidance to reflect that bulk clearing of the autocomplete list, or correcting the underlying contact, is now the realistic fix. Administrators should also flag the change to staff who relied on Contact Masking, because previously hidden contacts will simply reappear in their suggestions.
As a managed cloud provider, our view is that retiring a confusing feature is a defensible decision, but the way this one has landed is not Microsoft’s best work. The official line is that AutoComplete is unaffected, while the lived experience for a growing number of users is that the single most useful control in that area no longer works. SMEs should treat this as a small but real change in the risk profile of everyday email, not as a behind-the-scenes tidy-up.