Hi is there a limitation on the name of the actual O365 Tenant ? I know special chars have been enabled within sharepoint sites etc but is there a set of rules around whats allowed or not allowed at the actual tenant name level ?
The tenant name must be unique and it is the basis of several things including your SharePoint url. Basically, the rule of thumb is to get it as close to your org name as possible (I.e myorg.onmicrosoft.com) or something approximate to the use of 365 I.e myorg365.onmicrosoft.com
The biggest thing to understand is that this is permanent. You can’t change it after and if you want to you have to move to another tenant.
There are several good articles out there on this including
Well, you are right that you can use special characters in file names in SPO and even in site URLs. In regards of the name of the tenant, I think is the same case but behind the scenes some trimming is going to happen. For instance if your organization is Contoso Corporation, then internally you are going to have contosocorporation for SharePoint sites and also for the internal e-mail