Server Management

Sounds like you have a small environment so I would avoid setting up a Hybrid mode.  Too much of a hassle.

You may want to consider a 3rd party Office 365 reseller.  I chose AppRiver (www.appriver.com) because I used their Anti-SPAM system for years and they have always been quick with support and answers.  I have never had to contact Microsoft directly since I started partnering with them and I still use their Anti-SPAM instead of Microsoft's POS spam service.

Unfortunately I have not seen a step by step document on the best way to achieve this that is right for every environment, but can give you my two cents.

First, you obviously are going to want this to be easy to setup and easy to maintain.  I would suggest speaking with AppRiver and also a company called Okta to enable SSO with Active Directory integration.  When you speak with Okta ask for the Office 365 connect version which is free to connect AD to just O365.

For migrating the data, you are going to probably want to get a 3rd party app.  I used CodeTwo's exchange migration tool.  It was about $10 per user.  This is a steal when I think about how my last company paid Dell about $50K to migrate about 2000 mailboxes and it took about a year of planning to get it down.  I was able to pick up on how to use CodeTwo with just a few hours of cramming and testing.

The basic steps are:

• Have your O365 provider setup your tenant and licenses
• Configure your DNS Records except for MX and Autodisover
• (Optional but I recommmend) Setup our SSO and Directory integration.
• Start your mail migrations and wait for a day, week or more for your mail to move out.  It does not matter how fast your connection is because O365 throttles you to a max bandwidth.
• After your first pass of mail is complete schedule your final pass
• Cut over your Autodiscover and MX records some night.  I recommend during the week vs a weekend because if something comes up you at least have access to the users machines instead of dealing with phones and laptops remotely
• Perform the final push.  Applications like CodeTwo can sort out missing old mail without messing up any new messages that are just in the new mailbox.

Bottom line is if you are under the gun you are going to need some help.  Someone that has done this a few times should be able to get you going in just a couple of days.  The latest division I migrated only took a couple of days of work while the rest of the time was just waiting for mail.