Often connection limits are reputation based - known good senders get higher connection allowances than unknown or known-poor senders. This might be a good place to look at the number of connections you’re making from your dedicated IP while getting that message. I’d also look at the connections pooled over recent time periods. It’s likely this is just part of the warmup process and you’re going to have to finesse things for a few weeks during warmup.
laura > On 21 May 2026, at 10:27, SecOps, Dev via mailop <[email protected]> wrote: > > We're in the process of moving out of AWS SES Shared pool, into a dedicated > IP, and we're trying to build up reputation slowly but we're still hitting > some sporadic rate-limiting responses like below: > > 421 #4.4.5 Too many connections from your host. > > It would be great to know exactly what they expect so that we can comply with > the increase in volume. > > On Thu, May 21, 2026 at 11:00 AM Bram Van Daele (Teneo BV) <[email protected] > <mailto:[email protected]>> wrote: >> What specific SMTP responses are you getting from their border ? >> Skynet is particularly picky when it comes to simultaneous SMTP connections . >> >> >> >> From: mailop <[email protected] <mailto:[email protected]>> >> On Behalf Of SecOps, Dev via mailop >> Sent: Thursday, 21 May 2026 10:37 >> To: [email protected] <mailto:[email protected]> >> Subject: Re: [mailop] Transactional Email to Proximus' scarlet.be >> <http://scarlet.be/> - How to provide proof of High Volume Sender >> >> >> >> I'm sorry, I meant skynet.be <http://skynet.be/> >> >> >> >> On Thu, May 21, 2026 at 9:57 AM SecOps, Dev <[email protected] >> <mailto:[email protected]>> wrote: >> >> Hello List, >> >> >> >> This is my first email to the list. I'm wondering there's if anyone here >> from Proximus managing the rate-limiting queues of the scarlet.be >> <http://scarlet.be/> domain that could point me in the right direction. >> >> >> >> I can reach off-list from my professional .be TLD domain if that's a >> blocker. >> >> >> >> Best Regards, >> >> >> >> TIA, >> >> >> >> [email protected] <mailto:[email protected]> >> -----BEGIN PGP PUBLIC KEY BLOCK----- >> >> mDMEag66CBYJKwYBBAHaRw8BAQdAMNVdlzezcwCNwLaa9fsc3Jh+X7rCDOyHphgD >> FICOMhK0MVNSRURldiBTZWNPcHMgKG1haWxpbmctbGlzdHMpIDxkZXZvcHNAZGl6 >> b3JnLm5ldD6IkwQTFgoAOxYhBPpHG9wc7t+sdIXWcXraqS6BSNNEBQJqDroIAhsD >> BQsJCAcCAiICBhUKCQgLAgQWAgMBAh4HAheAAAoJEHraqS6BSNNEjRcBAPbEMYmZ >> 3gJpjk+3Roo1Ck5qjLFolQds3+0zQMXQgQ3QAQCO6AeBHPnKqvz4MArJfZODWras >> xft87BUm9wF+Q3OWArg4BGoOuggSCisGAQQBl1UBBQEBB0DI9NAzy+4PT28vFrsf >> wfDdujqMpL0yEmRcis3nUry6FQMBCAeIeAQYFgoAIBYhBPpHG9wc7t+sdIXWcXra >> qS6BSNNEBQJqDroIAhsMAAoJEHraqS6BSNNEQb4A/1mO9Qmu1mBzyI5OmPE0RIkP >> aKt/aG5EsWoLXTML3YyqAQDdAC0kzhAvN9jDSqCnxU8E6O9O7NXcaaHXMtbffyQu >> BQ== >> =phdp >> -----END PGP PUBLIC KEY BLOCK----- >> > _______________________________________________ > mailop mailing list > [email protected] > https://list.mailop.org/listinfo/mailop — Demystifying “It Depends...” since 2001 Laura Atkins Word to the Wise [email protected] Delivery hints and commentary: http://www.wordtothewise.com/blog
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