New Notes IDs must have 1024-bit or stronger RSA keys

When you register new Notes users, you must select at least a 1024-bit RSA key size for their Notes IDs.

RSA key sizes that are weaker than 1024-bit are no longer supported for new Notes IDs. Existing Notes IDs that use weaker key sizes are still supported, but you should consider using the key rollover feature to increase the key size for greater security. For more information, see User and server key rollover.
Note: If you attempt to register a user with a 630-bit key through an existing registration policy, a 1024-bit key is used and the following warning is displayed:
Registering users with less than a 1024 bit public key is no longer supported, 
1024 bits is now the minimum and will be used. Please update your registration policy.
As the message indicates, you should update your registration policy. To disable this warning message, use the following server notes.ini setting: ADMIN_DISABLE_REG_KEY_LENGTH_WARNING=1.