Dellaina,
I've been trying to invite someone and from the very first attempt,
their email keeps getting returned with the following message:
Deferred - 452 4.1.1 Too much mail from this address E2210
As Bruce and Frances have said, this has cropped up before.
I have a slightly different take on it, I don't think that the service is necessarily running out of capacity, but rather that "this address" is referring to Groups.io as a sender. So a rate limit is being applied on the suspicion that Groups.io is sending spam.
If I'm right what has to happen is that the service needs to recognize Groups.io as a mail list service and remove the rate limiting (or apply a much higher one, appropriate to a mailing list service).
How to make that happen though is unknown. I know that Mark at Groups.io does his best to track down deliverability problems, contacting the receiving services as necessary. But maybe a word to the service's technical support from their own users would help.
Shal
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