What's everyone using for Outbound fax?

I've completed several VoIP transitions in the past year or so but fax is one of those things that just wont die. Several of our clients still send outbound fax functionality -- who's the best provider? Our current provider that provides VoIP does not supply outbound faxing services.

So I'm looking for a third party that can do this for us.

I know I can get an ATA and hook up my fax machine to the PBX but this is pretty finnicky in my experience so I'd like to use an email-to-fax offering to ensure delivery and not mess around.