Hi @Sean Finley ,
Sorry, that's not possible.
Outlook's AutoComplete feature is designed to make sending email easier for senders. If you are worried about mistakenly selecting recipient addresses generated by Outlook's autocomplete feature, I recommend clicking "GAL" to select recipients when sending to internal users.
Thank you for your sincere suggestion and I submitted your feedback on the dedicated portal via the link below:
https://feedbackportal.microsoft.com/feedback/idea/4e9572ad-0f0c-ee11-a81c-000d3a7a48db
Many features of our current products are designed and upgraded based on customers’ feedback. With requirements like this increase, the problem may well be released in the future.
You can mark my reply as an answer, so that other users in the forum who have similar problems can also vote.
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