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Spam Resource: Microsoft errors: 5.4.4 (unable to route: no mail hosts for domain)
- August 22, 2023
- Posted by: Top Deliverability
- Category: Industry News Spam Resource
Al Iverson just shared a new engaging story on Spam Resource:
When sending to Microsoft OLC (Outlook Consumer – i.e. hotmail.com, outlook.com, msn.com, live.com, etc.) domains, are you seeing this bounce message?Microsoft: 5.4.4 (unable to route: no mail hosts for domain)If you’re seeing that error message, or something similar, here’s what’s happening, I think, based on what some smart folks have shared with me.All of those domains have an MX record that points to outlook-com.olc.protection.outlook.com. And when you look up the IP addresses for that server mentioned in the MX record, what do you get? Well, when I do it from here, I get just two IPs: 104.47.58.33 and 104.47.55.33.But other folks showed me examples where they were receiving 25+ IP addresses in response. I can’t reproduce it, so I don’t know if it’s geo-specific, intermittent, or if overall, the whole thing has been addressed. I suspect some combination of all of that. But anyway, I’m told that when the results
Read more: Microsoft errors: 5.4.4 (unable to route: no mail hosts for domain)
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