Invite external guests

I need to add our external vendor, Marco Rossi at Contoso, to next Monday’s procurement review as a guest. Invite Marco using his email marco.rossi@contoso.com, give him guest access limited to the 'Procurement Review' channel only, and set the guest expiration to 90 days. Confirm his invite was accepted before the meeting.

Before I invite this external vendor, make the guest experience frictionless: surface what files and channels Marco will see, flag any sensitive items that would be exposed, and suggest a brief note to include in the invite explaining access limits and who to contact if he needs broader rights.

I added consultant Sara Ahmed as a guest for the 'Design Reviews' channel but she reports a permissions error. I don't know whether her tenant blocks guest access, whether her email was added incorrectly, or whether the channel is private. What's the most likely issue and the quickest steps to verify and resolve access so she can join today's call?

We keep stalling projects because guest access trips security checks or fails to work. Where are we inconsistent—our provisioning steps, naming, or approval messages? Recommend one change to our invite process and one admin control to standardize guest onboarding and reduce friction without increasing risk.