Currently I have a simple mailto link that opens a user's default mail program; at the same time a modal appears on my user interface so that when the user returns they can select if they sent the email or not. However if the default email program is web based; like gmail; it will navigate the browser to gmail and the modal will never be visible. Worse than that they are navigated away from my site entirely. Setting _blank as the target would fix this issue for those people who have this type of default email client; but for others with Apple Mail or other standalone programs it opens a new tab.
I know I won't be able to determine what client they have; but it would be great to know what style client is about to open.