GMail itself will sometimes temporarily reject messages, then accept them later.
I have Postfix logs showing things like "this address is receiving a high rate of email" which are later accepted.
I have Postfix logs showing things like "this address is receiving a high rate of email" which are later accepted.
This is the reason I personally will not touch any Google services. And in business, I excise Google services as a priority. If a company cannot handle email in a civil manner, it certainly can't be trusted with anything of importance.