Once you've verified that your server isn't sending spam, you must submit the IP removal request to RBL. This article will provide instructions on removing your IP address from an RBL. Once the RBL remove from their list, the email sent from your server's IP address will be accepted at the recipient end.
You can use the following tool to check whether your IP is blocklisted or not,
https://www.accuwebhosting.com/resources/ip-blacklist-checker
Following is the blacklist-removal process.
Self-Service Removal: Many RBLs have self-service removal features that you can use to get your IP address off. Before doing this, make sure you have resolved all issues. You won't be able to remove your IP address from the RBL if your IP address is listed again.
Time-Based Removal: Most RBLs remove lower-level listings' IP addresses within a week or two. However, if the IP address sent spam more than once or in high volume, the period will be longer to remove the IP from the blocklist.
Gmail: How to Remove IP Address from Blacklist
If you have resolved the delivery and email authentication issues, Gmail usually removes your IP address from its blocklist within three to four days.
If your IP does not delist within 3-4 days, you will have to fill the form by accessing the following URL,
https://support.google.com/mail/contact/bulk_send_new?rd=1
Microsoft: How to Remove IP Address from Blacklist:
In Microsoft, you will have to place an IP removal request by filling the following form,
https://support.microsoft.com/en-us/supportrequestform/8ad563e3-288e-2a61-8122-3ba03d6b8d75
Yahoo: How to Remove IP Address from Blacklist
Yahoo uses the Spamhaus Blocklist Removal Center for the IP blocklist removal process. You can check the IP address status from the below URL,
https://check.spamhaus.org/
Office 365 Blacklist Removal Procedure:
You can use Office 365 IP blocklist removal form if your mail has been rejected due to your blocklisted IP address in Office 365. To request IP blocklist removal for an Office 365 email account, use the blocklist removal form by accessing the following URL,
https://sender.office.com/
Barracuda Central: How to Remove IP Address from Blacklist
You can use Barracuda Reputation Lookup to confirm your IP address on their block list. If your IP is Blacklist in Barracuda Central, you can place an IP removal request from the below URL,
https://www.barracudacentral.org/lookups
PSBL: How to Remove IP Address from Blacklist
You can visit the following URL and place an IP removal request from PSBL,
https://psbl.org/
That's it.