Can confirm on that one, Exchange / Outlook are the ones that play extremely well in this scenario. Microsoft learned these lessons very early on.... One hilarious example was internal to them in 1997, for instance (not the same type of problem, but still one of many things that they learned well early in exchange's life).
For all MS's faults, Exchange really is a damn good product at the end of the day if it's set up per documentation (ie: not a single server) and you actually use any of its functionality. It's the most set-it-and-forget-it and self-healing system outside of normal patching I've ever had to deal with at scale (largest of 70k users, smallest of 100 users). -----Original Message----- From: Ryan Hamel via NANOG <[email protected]> Sent: Tuesday, November 11, 2025 2:16 AM To: [email protected] Cc: Ryan Hamel <[email protected]> Subject: Re: [Ext] trolling Endre, Exchange only sends one reply to each sender (https://learn.microsoft.com/en-us/troubleshoot/exchange/client-connectivity/one-reply-sent-sender), and it's also configurable too (https://learn.microsoft.com/en-us/troubleshoot/exchange/email-delivery/understand-troubleshoot-oof-replies). Ryan Hamel ________________________________ From: Endre Szabo via NANOG <[email protected]> Sent: Monday, November 10, 2025 10:50 PM To: [email protected] <[email protected]> Cc: Endre Szabo <[email protected]> Subject: Re: [Ext] trolling Caution: This is an external email and may be malicious. Please take care when clicking links or opening attachments. On Mon, Nov 10, 2025 at 15:14:26+0000, Giorgio Bonfiglio via NANOG wrote: > Also, speaking about technical limitations - which mailserver in the world > does send one auto-reply PER MESSAGE to the same sender? I haven't seen this > in ages, most seem to be sending only once or at worst once every day or so. Oh, I know the answer to this one! It's a niche player in the market, and it's well known for not following standards or best practices. Like, they could have ignored messages with List-* headers, for example, right? The server in question is called Microsoft Exchange. _______________________________________________ NANOG mailing list https://lists.nanog.org/archives/list/[email protected]/message/BUZSGS4UJJTCCBMVNGCFM7UDKQSDQTDA/<https://lists.nanog.org/archives/list/[email protected]/message/BUZSGS4UJJTCCBMVNGCFM7UDKQSDQTDA/> _______________________________________________ NANOG mailing list https://lists.nanog.org/archives/list/[email protected]/message/BRXFVZBOV3TQZAFCV2IVOXEIXEL4DMSC/ _______________________________________________ NANOG mailing list https://lists.nanog.org/archives/list/[email protected]/message/QULMBW6OKPDS6B4TZ5OARL2W5XKPI3HF/
