In my application, I'm currently using mailto: links to open email compose dialogs. This is terrible for web mail users, since it typically causes Outlook or Apple Mail to launch into their setup wizard.
Until I've implemented a separate compose widget, I'm planning to special case the mailto links for users with Gmail/Yahoo/Hotmail/etc. addresses.
So far, I have the following compose link formats:
Gmail:
https://mail.google.com/mail/?view=cm&fs=1&tf=1&to=TO&su=SUBJECT&body=BODY
Yahoo! Mail (from StackOverflow):
http://compose.mail.yahoo.com/?to=TO&subject=SUBJECT&body=BODY
[Hotmail] (from StackOverflow)::
http://mail.live.com/mail/EditMessageLight.aspx?n=&to=TO&cc=CC&subject=SUBJECTt&body=BODY
Two questions:
- What's the correct format for AOL links?
- What other web mail clients should I support, and what format do they use?
Some searching led to this as the proper format for AOL Mail links:
http://webmail.aol.com/Mail/ComposeMessage.aspx?to=TO&subject=SUBJECT&body=BODY&cc=CC&bcc=BCC
Source: http://dev.aol.com/api/openmail/webmail (under 'External Invocation of Web Mail'), and some Google searching to find the parameters.
Once you have these 4 covered, I think you've got essentially all of the webmail clients covered.