Hi @Radu Ifrim
Thank you for posting your query on Q&A.
I understand that you want to add users from one tenant to another tenant without Outlook access to accept the invitation.
To answer your question yes, you can manually invite the guest user without access to email to achieve this you can use the Microsoft Entra B2B collaboration. This does not require the users to have an email account or access Outlook. They can join your tenant using a redemption URL.
I hope this answer helps! If you have any further questions, please feel free to ask.
For more information, please refer the below documents.
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