Classic Outlook does not die in 2027: what dies is your COM add-in
The date exists and it is official: March 2027, the opt-out stage for Enterprise environments, announced in Message Center post MC949965 and postponed from April 2026. But opt-out does not mean it is taken away: it is on by default and you can still switch back, with classic Outlook supported "until at least 2029". The public page describing the stages was revised three days after that announcement and still does not carry it. What you do control: the list of what does not cross over — COM add-ins, VBA, custom forms, on-premises Exchange — and the registry key that decides the day.
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