At the beginning of March, I started getting temporary rejections from gmail. Not all of my outgoing messages, maybe 1 in 10. Most of these messages were to one individual, to whom I've been sending for years. My domain has existed continously since 2002, and has never sent spam. The rejection message was startling: words to the effect of "Your message has been rejected because of the awful reputation of the sending domain". The reputation of my domain is spotless, according to various testing tools.

There have been no new rejections in the last two weeks.

According to TFA, Google started rejecting a proportion of mail from bulk senders in February. I wonder if I got caught up in some half-baked roll-out of this new (old) policy.