Mail Queue Option with Cut over day

The "Domain Move" add-on may help here: https://www.quest.com/products/on-demand-migration/#onesolutionmanyworkloadsplusad-24600266004004977

Also, if you want to be able to send and receive mail from Contoso.com in both Tenants during migration, we also offer a "Domain Coexistence" add-on.

Are they paid modules?  if not what will happen or how do we mitigate that?

My approach to this across 5 tenant migrations, the largest being 180 users has been to enable the mail forwarding from source to target and then do the cutover at a weekend.
There's the possibility mail could get rejected during the move of the domain but the tenants I have migrated are rather low on email throughput and this has worked well so far.

I'm still looking into a true solution to simply hold/queue the mail for this as the advanced mail flow options in quest aren't that well documented/explained IMO and I need to research further.

Domain move is included in the T5 Licensing and can be a standalone addon to T3 if you don't need the other T5 features.

FYI Domain Move is add-on to a T5 or a standalone item. It also has an SMTP host that collects any messages sent during the domain move process. 

lliversage said:

'm still looking into a true solution to simply hold/queue the mail for this as the advanced mail flow options in quest aren't that well documented/explained IMO and I need to research further.

What are you referring to with this "advanced mail flow options in quest ". Maybe I can field your questions.

FYI Domain Move is add-on to a T5 or a standalone item. It also has an SMTP host that collects any messages sent during the domain move process. 

lliversage said:

'm still looking into a true solution to simply hold/queue the mail for this as the advanced mail flow options in quest aren't that well documented/explained IMO and I need to research further.

What are you referring to with this "advanced mail flow options in quest ". Maybe I can field your questions.

ah, my bad, I thought it got included at T5, I recall the extra line item now for Domain Move.
Is queueing in the basic mode relatively new? - I'm sure when I last tried to use Domain Move that wasn't available and it only helped to move proxy addresses and register the domain in the tenant.

The advanced mail flow I was referring to was the coexistence advanced mode. The last time I tried to use domain move it wasn't a great experience, I ended up abandoning it and just scripting it up in PS and is in fact what I'm doing right now. Once the final OneDrive migration completes... Perhaps I need to revisit Domain Move and have a session with someone from Quest. - I need to get up to speed with the new Azure AD Device migration options too.