weeks ago I had to unblock a webdomain from SORBS.net. They listed my Website (IP) as a spam and we weren't able to write E-Mails to some most of our customers (mostly company-mail-addresses). So I delisted our Website and got unblocked. Now two or three weeks after that we are still blocked from the most Spam-Filter.
https://mxtoolbox.com/ is clean in blacklists and SMTP-checks.
What can I do that we reach our customers again? Is my IP still cached in their system and we have to wait until it gets refreshed (maybe in a month or a year)? If yes, is there a workaround I can do?