S3150 is the nauseating 500-level error, which is a permanent rejection. It has been lacking rhyme or reason since mid-January.
On Fri, Feb 20, 2026 at 5:54 PM, Matthew Pounsett via mailop<[email protected]> wrote: On Fri, Feb 20, 2026 at 5:01 PM Michael Wise <[email protected]> wrote: It’s throttling.Slow down your deliveries. The rate limit must be incredibly low, if that's the case. We sent less than 1500 messages to outlook.com mail servers all day on February 20th. If it is a rate limit, then please share where the rate limit is documented, so that I can set the throttle appropriately. I can't keep under a rate limit if I don't know what it is. And if it's a rate limit, why are we getting 500 errors instead of 400? That should be a temporary error. _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
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