[undecisive]

Well, certainly they haven't ruled it out. DNS servers are third-party servers. VPNs are third-party servers. They can be as kind or as nasty about this as they like,

For all my fear mongering, I should point out that the only reason Google are saying this is to cover their backs when they decide to levy the maximum fee on an unsuspecting competitor. If they don't consider you a direct competitor, you might be ok. They have no reason to use this policy to alienate the majority of desktop applications that connect to email.

But they also have no repercussions if they do.