Whenever we share anything like site collections or subsites the email option is selected by default and we have to uncheck it most of the time.
This post will help you to disable the default “send an email invitation”
Browse to this location on your sharepoint server.
C:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\TEMPLATE\LAYOUTS
And search for filename “aclinv.aspx”.
Edit in notepad or visual studio. Look for below labels and change the “Checked to False” it will be true by default.
After changing it save the file and refresh your SharePoint site.
Now, check the default and “send an email invitation” will be disabled.
Note
This has to be done on all SharePoint Servers and no iisreset or server restart is required.
Hope it helps.
Happy SharePointing.