Based on past experience, I'd suggest checking Google Postmaster Tools over the next few days to see if it gives any more clues. The report visibility is delayed, hence the mention of over the next few days. -Jeffrey
On Wed, Jul 3, 2024 at 5:24 PM Jason R Cowart via mailop <mailop@mailop.org> wrote: > I’m hoping someone from Gmail can reply off list. > > > > We (Stanford University—stanford.edu) are receiving a large number of > deferrals when trying to delivery to Gmail.com. The smtp code returned > is: > > > > 421-4.7.28 Gmail has detected an unusual rate of mail originating from > your SPF > > > > The best educated guess I can make as to that error is that when our > Office365 environment last weekend began doing SRS and rewriting the sender > address on forwarded messages (many users forward their M365 mailbox to a > personal Gmail address) this was as a spike in mail from our domain, > although the actual volume of mail should not have changed. > > > > In any case, the SRS was turned back off yesterday but we are still > effectively rate limited, with 20-30k messages pending delivery to > gmail.com. > > > > The response from the gmail.com help site was that if any mitigation was > warranted it would take two weeks and that there was no way to reply to > that “ticket.” > > > > Thanks, > > Jason Cowart > > University IT > > Stanford University > _______________________________________________ > mailop mailing list > mailop@mailop.org > https://list.mailop.org/listinfo/mailop > -- *Jeffrey Williams, Tech Lead* *Berkeley IT (bIT)* <https://technology.berkeley.edu/home> j...@berkeley.edu
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