Consider below point before Office 365 rollout:
Now most of planning for cloud solution because cloud solution is economically better than hosted services. Also no maintenance cost.
Office 365 is my got to solution and I am referring Office 365 to my current customer. It’s your choice…..
1. Office 365 License plans and features.
Select the plan as per your requirement. Check the pricing before make decision.
a. Office 365 Small Business
b. Office 365 Small Business Premium
c. Office 365 Midsize Business
2. Internet Bandwidth :
Less bandwidth is always problem for synchronization. Slow internet connection would make it impossible to upload Terabyte data per day to Microsoft’s data centers. Small organizations with lower bandwidth and a lot of data to move take longer to migrate from Exchange on-premises to O365. Without a high-speed connection, migration tools can help overcome this barrier by taking multiple passes over mailbox data before completing the actual cutover.
3. Calming security fears:
Migration to O365 is a controlled process with safeguards in place to ensure data is secure both during and after the transition. Currently multiple big companies are using same solution. Microsoft improves security drastically. E.g. MS is agreeable to signing liability paper related to specific compliance issues e.g. HIPPA.
4. Journaling will not work:
Issue that may come up is that journaling for compliance no longer works after migration to Office 365.
5. Existing Email Archiving doesn’t work:
Archive tool simply doesn't work (or work well) with Office 365. You move the mailbox to the cloud, which breaks the stubs, so users can't access those archived emails. Basically Microsoft providing good amount of data storage for Mailbox, SharePoint etc. may you not worried about archiving however what about old data.
6. The recipient rate limit per day 10000 (email send / receive limit).
Workaround: If you want to send email to over 10000 recipient then add recipient to distribution list and then send email.
7. There are no public folders in Office 365. Yes, it’s time to move to SharePoint. SharePoint is better choice than Public folder.
8. User get 10 GB of space plus 500 MB per user of shared storage.
9. No choice for Spam filter- Because Microsoft using Microsoft Forefront Online Protection for Exchange for Office 365.
10. By default gets @onmicrosoft.com email addresses. Outbound and inbound email domain changes are possible.
11. DNS setup is difficult if customer has other than Microsoft DNS server. Like Linux DNS server.
12. You may need to reset file server permission, if you are planning outsource Active Directory. Because some point you have decommission the Domain Controller.
Curtesy: MS O365 docs, 10 things you should know….