Email has been slowly balkanising itself for years now. By way of example, I know personally several people who run mail relays and not only refuse to relay messages from and to Google email servers but even refuse to _receive_ emails addressed to their users from GMail addresses. All of this on what is essentially a political objection.
In the fullness of time, email will fail as a communication medium because of these situations. I don't think that Google will mind terribly when it does.
It's not just political. I haven't taken that step but really sympathize with those that do.
Forwarding mail to Gmail accounts is perilous. My outbound queue is constantly full of mail to an established Gmail account that Google is throttling for some reason or another. I finally parted ways with a user over this specifically, since they had a number of mail accounts that were all forwarded to their Gmail account. For a company with so many smart employees, their handling on this is really dumb.
Receiving mail from Gmail accounts isn't much better. Spammers have discovered that they can cheaply spin up new Gmail accounts and spam the world for a good while before Google detects it. Since so many people use Gmail, on the receiving side I can't use any of the network reputation tricks to catch the spam. So, these days, an appreciable percentage of the spam landing in my users' mail accounts is coming from Google.
If it were just me, I'm pretty sure I'd just block anything to or from Gmail altogether and have one less recurring headache.
...which is really a shame, because I remember the excitement and wonder when Gmail debuted and how amazing it was at the time.
> I know personally several people who run mail relays and not only refuse to relay messages from and to Google email servers but even refuse to _receive_ emails addressed to their users from GMail addresses.
I don't refuse to relay messages to/from gmail addresses, but I do avoid interacting with gmail addresses as much as possible. The less I'm touching Google servers, the better.
Fortunately, most of the people I exchange email with don't use gmail.
In the fullness of time, email will fail as a communication medium because of these situations. I don't think that Google will mind terribly when it does.