Once I had to remove from the blacklists IP addresses of different dedicated servers located in data centers, since some mail services did not receive emails from them, due to the fact that the previous tenant did not use the IP address honestly or had viruses, spammed, and the current one got locks.
First of all, I recommend setting up SPF, DKIM, DMARC.
And also check for blocking for example with these services:
multirbl.valli.org
https://mxtoolbox.com/blacklists.aspx
https://mxtoolbox.com/public/tools/EmailHeaders.aspx
https://check.spamhaus.org
https://www.spamcop.net/bl.shtml
https://2ip.ru/spam/
https://www.virustotal.com
Further, I will describe how I contacted mail services and how quickly they unblocked (the IP addresses I requested to unblock, did not send spam for many years, but sent the previous owner of the IP address).
ivmSIP24 (deleted within an hour)
Request to delete by reference https://www.invaluement.com/removal/
cox.net (answered in an hour that they unblocked)
http://postmaster.cox.net/confluence/display/postmaster/Contact+US+Form
BarracudaCentral.org (deleted within an hour)
http://barracudacentral.org/lookups
The request to remove from the blacklist can be sent via the link
http://barracudacentral.org/rbl/removal-request
Sorbs
www.sorbs.net/lookup.shtml
You can contact the support link http://www.sorbs.net/cgi-bin/support.pl
Earthlink
I wrote an email on blockedbyearthlink @ abuse.earthlink.net with the subject Blocked 192.168.5.5, deleted from the list in two minutes, they said that the records will be updated within 24 hours.
The official instructions here are https://support.earthlink.net/articles/email/email-blocked-by-earthlink.php
ATT
I wrote on abuse_rbl @ abuse-att.net, received an auto-response that the appeal is considered and the link in the message https://www.att.com/esupport/postmaster/, if success is removed from the black list within 24-48 hours
MSN (@hotmail.com, @live.com, @msn.com, @live.ru, @outlook.com)
Unblocked, but the letters began to arrive in the spam folder, the support responded that this behavior is based on users voting on spam, if the spam will not arrive for some time, the letters will no longer fall into the spam folder.
Contact form – http://go.microsoft.com/fwlink/?LinkID=614866
Services – https://mail.live.com/mail/services.aspx
https://sendersupport.olc.protection.outlook.com/pm/troubleshooting.aspx
MegaRBL (www.megarbl.net)
I wrote through the form on the site (registration is needed) – removed from the list the next day.
CenturyLink.com (q.com)
I wrote on abuse@ centurytel.net)
https://www.centurylink.com/home/emailus/
Verizon / Yahoo
http://www2.verizon.net/micro/whitelist/request_form.asp?id=isp (whitelist application)
https://postmaster.aol.com/
icloud.com (Apple) (example 192.168.1.1)
https://support.proofpoint.com/dnsbl-lookup.cgi?ip=192.168.1.1
Comcast
www.comcastsupport.com/rbl
Gmail
Recommendations http://www.google.com/mail/help/bulk_mail.html
http://mail.google.com/support/bin/request.py?contact_type=bulk_send&hl=en
LashBack
https://blacklist.lashback.com/
t-online.de
The mail server returned an email with a delivery error and the message “refused to talk to me”, and a contact email was written next to it for clarification. I wrote a message to it and they replied to me on the same day that they reset the reputation for the IP address and that the changes will be applied within 24 hours.