Hi @Anonymous ,
Could you please share a bit more about your Gallery? Does it connect to a SP Library?
Do you want to auto-mail the file in your Gallery when you press the ">" icon?
Further, could you please show more details about the file that you mentioned? Is it a Image or other doc file (e.g. PDF, Excel, Word, ...)?
If your Gallery is connected to a SP Library, and you want to auto-mail the file in your Gallery when you press the ">" icon, afraid that there is no way to achieve your needs in Power Apps canvas app itself.
As an alternative solution, I think the combination of Power Apps and Power Automate flow could achieve your needs. You could consider fire a Power Automate flow when you press the ">" icon in your Gallery, then use the Power Automate flow to send email.
You could pass the File Identifier of the selected file in your Gallery from your canvas app to your flow, then within your flow, add a "Get file content" action of SharePoint Connector to get the file content based on the passed File Identifier.
Please take a try with the following workaround:
Flow's configuration as below:


App's configuration as below:

Within your canvas app, you need to create a connection to your above flow from your canvas app firstly. The set the OnSelect property of the ">" icon inside your Gallery to following:
'Your Flow Name'.Run(ThisItem.Identifier)
After that, when you press the ">" icon in your Gallery, it would fire the flow to send an Outlook email along with corresponding file as attachment.
More details about firing a flow from a canvas app, please check the following video resource:
https://www.youtube.com/watch?v=1wl9AtxWdkg
Best regards,