Hi @Glenn Maxwell ,
Welcome to our forum!
According to your description, i notice that the issue only occurs in AVD, in order to further confirm if the issue is related to Outlook client, it is suggested that you could try to delete the current Outlook profile and create a new profile(Control Panel>Mail>Show Profiles>add) and add the account for testing to check if there are some differences.
If i delete the OST file on my AVD will it fix the issue, will my emails gets deleted?
As i know, the ost file is the data file of your account, you can try to archive to reduce the size of your mailbox size. More information: Archive in Outlook for Windows.
Hope to help you!
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