Hi Aja Simpson Zulfiqar,
Thanks for posting in our forum. For your problem, my answer is yes. You can recall the email send via mail merge. However, the recipient have to be a user who has an Office 365 or Microsoft Exchange email account in the same organization
as yours.
If you meet the requirements, you can refer to the article below to recall the message:
https://support.office.com/en-us/article/recall-or-replace-an-email-message-that-you-sent-35027f88-d655-4554-b4f8-6c0729a723a0
If it doesn’t work for you, to better help you, I’d like to collect some detailed information as below for further investigation:
1.
What's the version of your Outlook? You can provide us a screenshot about your product information. (File > Office Account > Product Information)
2.
Can you see the email sent via mail merge in the sent items folder of Outlook?
3.
Can you make sure that the recipient hasn’t read the email?
Best Regards,
Huni