slow mail and relayhost to office365?

[Tom Horsley]

I'm already running postfix on my Fedora desktop here at
work to mostly deal with local mail generated by cron, etc.

Now the powers that be have migrated us to office365 "cloud"
mail, and every time I send mail I get to sit like a lump
staring at the "authenticating" dialog for 15 or 20 seconds
while my mail client talks to the office365 smtp server.

If I go to the trouble of setting up postfix with a relayhost
to point to the office365 server, will that allow postfix to
be the place where are the delay happens in the background
so I don't have to stare at it in my mail client any longer?

I just want to be sure the mail really will go in a queue and get
processed in the background before I go to all the trouble
of trying to configure the relayhost :-).

(And if anyone already has an smtp.office365.com relayhost
configuration they could point me at, that would be nice
as well :-).