Hi @Guy Franco
There are multiple attributes used to name an object in AD, as you can see from below, they have different maximum lengths. When you create an OU object in ADUC, the maximum length of the name is based on the max OU length - 3 characters, to accommodate the rDNAttID i.e. 'ou='. However, once the object is created, you can rename the OU in ADUC, and you can exceed the 64 character limit and the name can be up to 256 characters - 3 characters.
Once you exceed the max length for the OU, the OU attribute will be truncated to its maximum length, which can cause duplicate name issues.
Gary.