I've had some issues with domain mapping and
FORCE_SSL_ADMIN. Here's the situation:
("Remote Login" and "Redirect administration pages to site's original domain" are enabled.)
I have a site mapped to
mysite.com, and its original url is
mysite.mynetwork.com. So far so good. I've set
true. The problem is that when I'm on
mysite.com and I click an administration link (from within the admin bar, or my theme), the url is
https://mysite.com/wp-admin/... which isn't configured on my server (that's why I am redirecting admin pages).
So here's my solution:
Basically, rather than redirecting to the original url on
admin_init it ensures that all admin links generated by WordPress already use the correct URL. I haven't tested it extensively yet, but it seems like it's doing the job for me.