Hi @Alanna Cole ,
For further confirm your issue, please provide some information:
(1) Does your template contain large size attachment?
(2) How did you create and use it? I have tried to create a template via New E-mail> File > Save as> Outlook Template on my outlook2016 and use it via New Items> More Items> Choose Form> under User Template files, choose my template(.oft) file, it could work normally in Outlook client.
It’s suggest to create a new template by the above steps to see if it could work normally.
(3) What’s the version of your Outlook? (File> Office Account> About Outlook)
According to my search, the issue usually occurs due to some third-party Add-ins. Please run Outlook in safe mode and see whether this issue continues. For detailed steps, you may refer to the “Start Outlook in safe mode and disable add-ins” section in this document.
In addition, I found a similar thread, you can focus on the option("Adobe Send & Track for Microsoft Outlook - Acrobat")in this discussion.
If this doesn’t help, personally I’d recommend creating a new profile.
(1) Exit Outlook.
(2) In Control Panel, click or double-click Mail.
(3) Choose Show Profiles> Add. In the Profile Name box, type a name for the profile, and then choose OK.
(4) Add your account to test if the problem is resolved.
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