If you are unable to send email to Outlook, Hotmail, Live, or Microsoft 365 addresses, first check your mail server logs for the exact error returned by Microsoft.
Errors like the following usually mean Microsoft is blocking or rate-limiting mail from your server's IP address:
550 5.7.1 Unfortunately, messages from [your IP address] weren't sent. Please contact your Internet service provider since part of their network is on our block list.
In this context, Microsoft generally expects the operator of the sending mail server to investigate and submit any delisting request. For a customer-managed VPS, that is you or your system administrator.
This can happen even when you are not sending spam. Microsoft assigns reputation to sending IP addresses, and that reputation has to be earned over time. Servers that send little or no mail to Microsoft-hosted recipients can have a low default reputation, which makes them more likely to hit Outlook/Hotmail delivery blocks.
BinaryLane cannot directly remove an IP address from Microsoft's blocklist, and changing IP addresses is not usually a reliable fix. A new IP address may have the same issue until it builds its own sending reputation.
Request delisting from Microsoft
Microsoft uses related but separate systems for Microsoft 365 hosted mail and Outlook.com consumer mail. Match the delisting path to the bounce/error you are receiving.
For Microsoft 365 or Exchange Online recipient addresses, especially where the bounce mentions 550 5.7.606 through 550 5.7.649 or directs you to Microsoft's delist portal, submit the affected IP address and latest bounce/error message here:
If Microsoft confirms the IP will be delisted, delivery may still take time to recover. Microsoft documentation notes that restrictions can take up to 24 hours or longer to be removed.
If the bounce shows 550 5.7.511, Microsoft says the normal delist portal cannot resolve that block. Forward the full bounce message, including the IP address, to delist@microsoft.com.
For Outlook.com consumer addresses such as @hotmail.com, @outlook.com, @live.com, or @msn.com, use SNDS to review the IP reputation and use Microsoft's Outlook.com sender support form if mail is still being blocked. A successful sender.office.com request does not necessarily clear an Outlook.com/SNDS reputation block.
https://go.microsoft.com/fwlink/?LinkID=614866
Monitor your Microsoft sender reputation
You can add the IP address to Microsoft's Smart Network Data Service (SNDS), which may provide reputation and traffic information for mail sent to Outlook.com consumer recipients:
https://substrate.office.com/ip-domain-management-snds/SNDS/AddNetwork
Enter your server's IP address and follow Microsoft's delegated access process. If Microsoft asks you to select a delegated access request email address for the network, choose `ABUSE@MAMMOTHMEDIA.COM.AU`.
If SNDS shows the IP as blocked, treat that as an Outlook.com reputation/blocking signal. Investigate the mail source, correct any abuse or authentication issues, and contact Outlook.com sender support if the block remains.
Improve deliverability
If reliable email delivery is important for your business, consider using a dedicated third-party SMTP relay or transactional email provider. These providers specialise in mail delivery and usually have established reputations with Microsoft and other large mail providers.
Examples include services such as SendGrid, Postmark, Mailgun, Amazon SES, or similar SMTP relay providers.
You should also ensure your domain and mail server are configured correctly, including:
- Valid forward and reverse DNS for the sending IP address
- SPF records authorising your mail server or relay
- DKIM signing for outbound mail
- DMARC policy for your domain
- A mail server that does not permit open relay or unauthenticated outbound spam
These records do not guarantee Microsoft will delist an IP, but they are expected for normal mail delivery and can help build reputation over time.