Short answer is (likely) that your mail provider (Gmail) is rejecting posts to user@p.a.o which hit its spam trigger but did not hit the ASF's spam trigger.
This triggers the mailing list to tell you that a message it tried to send you was rejected. So, you get a warning about a message that you never saw in the first place. But, as Ted says, just ignore it. On Feb 20, 2017 09:47, "Ted Yu" <yuzhih...@gmail.com> wrote: I received such message as well. You can ignore it. On Feb 20, 2017, at 5:46 AM, Cheyenne Forbes <cheyenne.osanu.forbes@gmail. com> wrote: Hi! This is the ezmlm program. I'm managing the user@phoenix.apache.org mailing list. Messages to you from the user mailing list seem to have been bouncing. I've attached a copy of the first bounce message I received. If this message bounces too, I will send you a probe. If the probe bounces, I will remove your address from the user mailing list, without further notice. I've kept a list of which messages from the user mailing list have bounced from your address.