You want to move to Domino? You need a plan!

Cloud services are all en vogue, the hot kid on the block and irressitible. So you decided to move there, but you decided your luggage has to come along. And suddenly your realize, that flipping a switch won't do the trick. Now you need to listen to the expert.
The good folks at Amazon have compiled a table that gives you some idea how much it would take to transfer data:

Available Internet Connection	Theoretical Min. Number of Days to Transfer 1TB at 80% Network Utilization	How much data do you have: TB
T1 (1.544Mbps)	82 days
10Mbps	13 days
T3 (44.736Mbps)	3 days
100Mbps	1 to 2 days
1000Mbps	Less than 1 day	Some stuff for your math

(Reproduced without asking)
Talking to customers gung ho to move, I came across data volumes of 10-400 TB. Now go and check your pipe and do the math. A big bang, just flip the switch migration is out of the picture. You need a plan. Here is a cheat sheet to get you started:

1. Create a database that contains all information of your existing users and how they will be once provisioned on Domino (If you are certified for IBM SmartCloud migrations IBM has one for you)
2. Gather intelligence on data size and connection speed. Design your daily batch size accordingly
3. Send a message to your existing users, where you collect their credentials securely and offer them a time slot for their migration. A good measure is to bundle your daily slots into bigger units of 3-7 days, so you have some wiggle room. Using some intelligent lookup you only present slots that have not been taken up
4. Send a nice confirmation message with date and steps to be taken. Let the user know, that at cut-over day they can use the new mail system instantly, but it might take a while (replace "while" with "up to x hours" based on your measurements and the mail size intelligence you have gathered) before existing messages show up
5. When the mailbox is due, send another message to let the user kick off the process (or confirm her consent that it kicks off). In that message it is a good idea to point to learning resources like the "what's new" summary or training videos or classes
6. Once the migration is completed, send another message with some nice looking stats and thanking for your patience
7. Communicate, Communicate, Communicate!

The checklist covers the user facing part of your migration. You still have to plan DNS cut-over, routing while moving, https access, redirection on mail links etc. Of course that list also applies for your pilot group/test run.
As usual: YMMV