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by zahllos 930 days ago
Outlook are a pain. If you don't regularly send email to outlook.com they forget your IP and start responding with 550s.

I have a daily message sent out from my server to a test account at outlook.com for two reasons: to try to work around this behaviour and to know immediately when there is a delivery issue.
1 comments
sbuk 930 days ago
> Outlook are a pain. If you don't regularly send email to outlook.com they forget your IP and start responding with 550s.

All providers should be doing that. Most will remove IPs/domains after 90-120 days.

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zahllos 929 days ago
Disagree. They can do what they want with the email once it is in their queue but bouncing 'unknown' IPs is an extreme choice especially when they have SPF/dkim/dmarc/mta-sts/... all set up, and are not on any spam lists, and are hosted in a reputable data centre.

SMTP 550 means the email bounces. The sender knows but unless they're also the admin they can't do anything about it. The recipient knows nothing. In the most recent case that happened to me, it happened when I sent a reply to an @outlook I had just received a message from (and was regularly receiving emails from, but only rarely needed to reply).

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