This browser is no longer supported.
Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(134.4, 18%, 23%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EJA%3C/text%3E%3C/svg%3E)
Hi, I use Microsoft Outlook to send and receive emails. This works for most email addresses, however when I send an email to a "@outlook" address it bounces. Can you please advise how this can be fixed. thank you
Using Classic Outlook on Windows for personal email, calendar, and contact management
I read all your suggestions and they do not apply. Can anyone assist with this issue please
Answer accepted by question author
Hello, can you please share the bounce email? It contains important diagnostic data that helps shed some light of the root cause. Feel free to redact personal information when you share.
host outlook-com.olc.protection.outlook.com [52.101.41.7]
SMTP error from remote mail server after pipelined sending data block:
550 5.7.1 Unfortunately, messages from [103.150.252.204] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to [http://mail.live.com/mail/troubleshooting.atruncated]
Thank you for sharing this.
The IP used by your email service provider is in a blacklist. This means this IP or this IP range has been detected with increased abuse activities. You need to let your email service provider know. They need to tighten outbound spam filters to improve IP reputation score before Microsoft would let their emails in.
I had contacted OPTUS and they said it was a fault with MS Outlook ??? so dont know where to go from here. thanks for your help
Jo Ann, that’s very disappointing to hear. I’m sorry you got caught in the middle. I wish I could help you, but there’s absolutely nothing Microsoft can do on their side. What I can do is make sure you have enough information to take back to Optus, because they’re clearly missing some basic knowledge in this area.
At the end of my message I attached a screenshot showing that their sending IP address is on a blacklist (you can drag this image into a new browser tab to view it full size).
If an IP shows up on a blacklist, it means that IP has recently been a source of spam or other abusive traffic (often due to a compromised server, an open relay, a misconfiguration, or spam-trap hits). This does not mean you are spamming anyone. It means the IP address used by Optus’s email service has a poor reputation.
S5H is one of many third-party organizations that monitor IP reputations. Think of it like the Better Business Bureau for email sending reputation. If a business operates poorly, it can get a bad BBB rating. Similarly, Microsoft (and many other email providers) may use third-party blacklists as signals when deciding whether to accept or reject incoming mail. Because Optus’s sending IP is blacklisted by S5H, Microsoft is rejecting their emails to Outlook/Hotmail users. Microsoft will not accept those emails until Optus improves the IP reputation and the IP is removed from the blacklist.
As for how to fix it, that is not Microsoft’s responsibility, and Microsoft has no control over it. Optus needs to take the necessary steps, such as tightening their outbound spam filtering and addressing any abuse on their network. Once the abusive/spam volume drops, the IP reputation should improve, and Microsoft may begin accepting their emails again.
I really hope this helps clarify what’s going on.
thank you so much for this information :)
Apologies for the small print above. that is the response I received. Jo :)
This is the 'bounce' email response