Hi @Anonymous,
Do you want to send an Outlook email to a specific user within your PowerApps app?
I assume that you want to send an Outlook email to a specific user within your PowerApps app, I think there is something wrong with the formula that you provided.
If you want to send an outlook email to a specific user within your PowerApps app, you should create a connection to Office 365 Outlook and add it as a data source within your PowerApps app firstly. More details about sending emails via Office 365 Outloook within PowerApps, please check the following article:
Send emails via Office 365 Outlook within PowerApps
I have made a test on my side and please take a try with the following workaround:
The OnSelect property of the Button control set to following formula:
Office365.SendEmail("Test3@xxxxxx.xxmicrosoft.com","Send email from PowerApps","Item: "&Concat(ComboBox1.SelectedItems,First_x0020_name&" "))
The received email shows up as below:
Best regards,
Kris