On Sun, Apr 5, 2020 at 05:43 PM, Niman H wrote:
Their email delivery history shows many responses of
": 550 5.1.0 <66.175.222.12> This IP has sent too many messages this hour. IB504 <>"
66.175.222.12 is the IP address of Groups.io's outbound mail server.
Some Mail Service Providers suddenly take it upon themselves to bounce Groups.io mail for reasons nobody really knows; getting an MSP to admit to this is likely to be tricky. One blind spot is that any group owner can only see bounces for their own group; there is no means of knowing (without asking the individuals concerned) how many groups they subscribe to and how many emails they receive as a result. "Too many messages" is a somewhat unclear description of the problem; how many
is too many!
Check your members' mail providers (the Bouncing list is a good place to start) to see if there is anything that might be statistically significant.
Chris
