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You should try the SocialSharing Plugin
from the Verified Plugins Marketplace. Along with sharing to social media, It supports starting a mail app with all the possible mail settings, attachments etc. Once you have installed the plugin in your project and the deviceready event has fired, you can use the following piece of code to start the default email app with the corresponding mail content:
// check for a configured email client
// share something
// TO: must be null or an array
// CC: must be null or an array
// BCC: must be null or an array
// called when email was sent or canceled, no way to differentiate
// called when something unexpected happened
As a file attachment you can also use the device file path string or the base64 string path of the file.
On the SocialSharing Plugin page, you can click "Try Plugin in AppBuilder" and it will load the plugin's sample app where u can test the functionality.
I hope this solution works for you. Let me know in case you experience any problems or have any further questions.