Knowledge Base Hub

Browse through our helpful how-to guides to get the fastest solutions to your technical issues.

Home  >  Email FAQ  >  What is Blacklisting & IP Address Reputation?
Top Scroll

What is Blacklisting & IP Address Reputation?

 4 min


The article gives details about IP address reputation and blacklisting. These can have an impact on the emails you send.

Related article: How to Keep Email Out of the Spam Folder?

What is IP Address Reputation?

IP address reputation finds out whether emails sent by a domain are genuine, spam, or junk mail. Many factors might cause an IP address’s reputation to grow or fall.

The following are some of the most common reasons:

  • The number of emails sent.
  • The number of emails sent that receivers delete unread/ without reading.
  • The number of spam tagged emails sent.
  • The number of emails sent to the wrong address.

What is blacklisting?

Blacklisting is a technique for detecting suspicious email activities. Cybersecurity firms maintain records of IP addresses used to send spam emails. These blacklists assist hosting companies in identifying and blocking problematic senders’ emails.

Why is my email sent to spam or junk mail on large providers?

Every large email and hosting service provider filters unsolicited and undesired emails and automatically delivers them to users’ trash or spam mail folders. Even if the user requested to receive the emails, ISPs send them as trash or spam.

Large providers do not actually share standards for detecting trash or spam mail. The following are some of the most prevalent reasons:

  • Reputation/Age — A new account or one that has sent hundreds of emails may be flagged by an email or hosting provider. Gmail, for example, sends all incoming emails to the spam bin until its reputation improves.
  • Blacklist– A blacklist may contain your IP address, hostname, or transmitting domain.
  • Content — Certain words or phrases in an email may be filtered by an email or hosting provider.
  • Links — An email or hosting provider may filter an email to prevent it from including links to banned domains.
  • Source — If other email messages received from the same IP address are spam, an email or hosting company may label your email as spam. This can be an issue for small email senders who are on the shared servers.
  • Headers – If the From and Reply to addresses and domains are inconsistent, an email or hosting provider may mark your email as spam.
  • Engagement – While recipients can mark emails as spam, engagement metrics have an impact on the email-filtering process. Such engagement metrics are being used by an increasing number of Internet service providers (ISPs), including Yahoo! and Gmail, to evaluate whether to block or filter an email. Google utilizes engagement metrics to determine whether or not a user wants emails from a sender. Users’ interactions with email are tracked using engagement metrics.

An email or hosting provider, for example, may keep track of:

  • Opened emails
  • Deleted emails that were unread 
  • Emails with hyperlinks

How can I find out whether mail from my server has been blocked?

To see if your IP address, hostname, or sending domain is on any existing blacklists, use the following resources:

To check IP addresses, use the following resources :


Some current real-time blackhole lists (RBLs) may arbitrarily ban your server’s IP address. As an example:

  • A country may prohibit the IP address of the server related to other countries.
  • Except for one country, the country prohibits IP addresses from all other countries.
  • A provider-specific measure may cause the blacklist to ban your server’s IP addresses.

How to check IP address reputation?

Here are a few resources that give up-to-date information for determining the reputation of an IP address:

Email providers use IP addresses and domain reputations to determine the history of suspicious emails. This data assists users in identifying undesired or unsolicited email sources.

How do I fix the reputation of my IP address with an email or hosting provider?

  • Gmail

First, review Gmail’s instructions to figure out why Gmail banned your email attempt. If Gmail continues to flag your emails as spam, you must contact the Gmail Team directly by completing the Bulk Sender Contact Form.

  • Microsoft® products (Outlook®, Hotmail®, and Yahoo)

Microsoft’s error response advises contacting your hosting provider since this problem might signal a network-wide block. Direct your provider to Microsoft’s Troubleshooting page. You can contact Microsoft’s mail services if you are experiencing delivery problems.

  • Office365®

Read Microsoft’s non-delivery report error documentation for additional details. Through the Office 365 Anti-Spam IP Delist Portal, Microsoft gives instructions on how to be removed from their ‘banned senders’ list.



For our Knowledge Base visitors only
Get 10% OFF on Hosting
Special Offer!
Claim the discount before it’s too late. Use the coupon code:
Note: Copy the coupon code and apply it on checkout.