Domain and IP reputation
During email delivery ISP's filters check your sending domain's and IP's email sending reputation. Filters check both domain and IP history, but mainly your email sending IP determines whether your email can be delivered. Today the poor IP reputation is still the #1 reason for soft bounces.
If you don't run your own mail server, but using an online email sending tool for delivering your emails, you might not even know what IP address your emails are sent from, and probably don't know anything about the IP's email sending history.
How to check IP reputation
Find out your IP address
Go to https://www.mail-tester.com/ and copy their test email address. Send a copy of your campaign to their test email address. Make sure you use the same email sending application with the same setting as you use for sending your campaigns.
Once you sent a copy of your campaign to that email address, click on check your score on Mail Tester.
In the blacklist section, you can find the IP address your email had been sent from. It looks like this: 100.110.120.130 . Copy this IP address.
Check if the IP address is listed on any blacklists
Mail Tester checks the IP Address against the most common blacklists. But I suggest you go further. Visits https://mxtoolbox.com/blacklists.aspx . Paste your IP address and click on blacklist check. MX Toolbox will search almost 100 blacklists if the IP address is listed.
If the IP is listed on any blacklists, it is likely to affect your email delivery and inbox rates.
Check IP’s email sending history
SenderScore is operated by Return Path. Visit https://senderscore.org/ to check the IP’s email sending history.
Create a free account to see the details. Once you are logged in enter the IP address on the homepage and click on ‘View report”.
SenderScore shares data with large ISP’s. From this simple report we can see how many emails are being sent from the IP, are there any issues with the email emails being sent. If there are any issues why is the IP scored down, e.g. blacklists, hitting spam traps or too many invalid recipients. You can also see what domains are using this IP for email sending.