In today's digital environment, email service providers continually strive to protect their users from spam and unwanted mail. One commonly employed measure is the blocking of IP addresses from which suspicious communication originates. This article focuses on the specific issue of email delivery to Outlook.com platform from an IP address that has been blacklisted by the Internet Service Provider (ISP).

Problem

The email server reports a 550 5.7.1 error when attempting to send an email to an Outlook.com address. The error message is as follows: "Unfortunately, messages from [85.118.130.105] weren't sent. Please contact your Internet service provider since part of their network is on our block list." This indicates that the sender's IP address has been listed on the email service provider's block list, preventing message delivery.

Causes

The inclusion of an IP address on a blacklist can be attributed to several factors:

1. High email volume: Excessive emails sent from a single IP address may raise suspicion of spam.
2. Email content: Emails containing phishing links, malware, or other harmful content can lead to blacklisting.
3. User complaints: If users mark incoming emails from a particular IP address as spam, it can result in its blocking.
4. Misconfigured DNS records: Incomplete or improperly configured SPF, DKIM, and DMARC records can cause issues with sender authentication and credibility.

Solution

To resolve the issue and restore the ability to deliver emails to Outlook.com, the following steps should be taken:

1. Check IP address on blacklist: Utilize online tools like MXToolbox to verify if your IP address is blacklisted.
2. Review email practices: Ensure that your email campaigns do not contain spammy content and adhere to best practices for bulk email sending.
3. Configure DNS records: Make sure that your SPF, DKIM, and DMARC records are correctly configured to enhance the authentication of your emails.
4. Request removal from blacklist: Contact Outlook.com's technical support with a request for a review of your IP address and its removal from the blacklist. Provide evidence that you have addressed the reasons that led to its blacklisting.

The issue of email delivery to Outlook.com from a blocked IP address requires careful analysis and the adoption of specific measures for its resolution. Proper configuration of DNS records, review of email practices, and communication with the email service provider are crucial steps towards restoring trust and ensuring smooth email delivery.