Hello, just my opinion but I find the way of adding a mail from Gmail to Asana a bit quirky, having to send it to x@mail.asana.com.
Couldn’t you supply through your Chrome extension a way to just press a button within the Gmail client instead? Something like AODocs has in their integration (as shown in the image included)? Your Chrome extension only makes it possible to copy subject and a url to the e-mail into a task, which isn’t the same as sending to x@mail.asana.com.