I've had the same issue with newly generated keys in ISPConfig. My DNS is Linode and they seem to have the issue were they don't parse the quotes properly. When doing a DKIM check on MXtoolbox, the syntax is reported incorrectly and looking at the value, you can see it containing ;" in the string! : Code: v=DKIM1; t=s; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA1L1rCF6xrzim2Lt1+Zt2PZ/J3GPhqDAqNCUXvosDcbMXRfEryzN1pz9V84curAynauRkDotzGy4XSkuGInzmEp0frMtBwLxcdpndMnadONjYLEnOnbutjHUqFgK3a4pyInachk0RYH2c""W/JJuNx42MXbDaMvBGABfArVji/Bmi9LqJ68gTAduuUJqhfVLmUMEBPUW4voaMkt7xXo/Ap5YEsgQoeAF1stgI9KY31xWzuBHZGxZDN2nO+gDRVCwpUyDNp3qFrpnWcOnCeaKhN3iQiYk8y5zKHipgyAGTd3YxykaDjOubFlowNBK4itDTCs4iQMQN2/i/N350EKagHw""+QIDAQAB Manually removing the quotes at the Linode DNS end fixes the problem.
I use joker.com for DNS and I have to remove " characters from the public key for it to work. ISPconfig usually add's "" on two different places within the public key. Remove those and and you are good to go.
