as shown above ISPConfig outputs this DKIM for my mail domain "v=DKIM1; t=s; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCkboodfbdcpyMil+NSYU/J20xopXRnpiqqKGsw6C8uF7kqCBOSwhFpKHnSVHvH6xBHlCO8c4KyIJIP1hL92PFm2MPhVvdtpmt2Q7JjJFky94NMGn4YrRgw8oO28dxAmLe7c7NBCR27ph2MR19O""Nf56xzmp1XpfFLpWB8gFWfvzlwIDAQAB" i shortened it to v=DKIM1; t=s; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCkboodfbdcpyMil+NSYU/J20xopXRnpiqqKGsw6C8uF7kqCBOSwhFpKHnSVHvH6xBHlCO8c4KyIJIP1hL92PFm2MPhVvdtpmt2Q7JjJFky94NMGn4YrRgw8oO28dxAmLe7c7NBCR27ph2MR19O""Nf56xzmp1XpfFLpWB8gFWfvzlwIDAQAB ( but my dns provider does not accept "" , the input field suggest to put a \ before the ") i shortended it a second time to v=DKIM1; t=s; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCkboodfbdcpyMil+NSYU/J20xopXRnpiqqKGsw6C8uF7kqCBOSwhFpKHnSVHvH6xBHlCO8c4KyIJIP1hL92PFm2MPhVvdtpmt2Q7JjJFky94NMGn4YrRgw8oO28dxAmLe7c7NBCR27ph2MR19O ( now the entry is valid for input, but seems to be not an valid RSA code) provider DNS settings on dkimcore.org/c/keycheck i get This doesn't seem to be a valid RSA public key: RSA.xs:178: OpenSSL error: too long at blib/lib/Crypt/OpenSSL/RSA.pm (autosplit into blib/lib/auto/Crypt/OpenSSL/RSA/new_public_key.al) line 91.
Seems the DKIM format is not set in stone, some players accept one way, others some other. This has been discussed previously. For example on this thread: https://forum.howtoforge.com/threads/invalid-format-of-dkim-record.85500/
DKIM keys become invalid, so shortening must break them. If your provider does not support split DKIM records, then just remove the "" inside the key, but do not shorten it!
