Migrating On Premise Exchange Server 2010 SP3 to Exchange 365 with no downtime or issue to users ?


I'd like to know if anyone here can share your experience in migrating the Exchange Server on premise to the cloud (Office 365) with no downtime or issues to the end users.

My current situation:
Single AD domain
Exchange Server 2010 no DAG hosting 5000 mailboxes for 3000+ users online in multiple different geographical location in Australian continent and some few thousands in Europe Continent,
All email older than one year old is automatically archived by Symantec Enterprise Vault v10.

Can anyone please clarify my points below:

1. For High Availability, all mailboxes migrated to Office 365 will not require the Internal IT Staff to create or worry about DAG it will always be online with high availability in all different continent.

2. No need to worry about Windows Update to the Exchange Servers as this is fully transparent to the users and internal IT staff

3. Office 365 Exchange will not have any bug or issues with calendaring and delegate mailboxes since all mailboxes in the Office 365 will be patched automatically by Microsoft hence will be trouble free.

4. All email or mailboxes can still be downloaded for .PST offline archive using Powershell or fully archived by in house/on-premise Symantec Enterprise Vault.

5. migrating 13 TB+ of exchange mailbox DB can be done automatically by using Powershell to export / move mailbox over the business hours with no downtime.

6. email access and response for users located in different continent will be speedy with no lag since the Exchange on Office 365 is always available and accessible everywhere around the world.

Are those assumptions correct for hassle free Exchange server migration to cloud ?
I need to convince my manager that is the case with cheaper option of using Office 365 rather than managing it in house.

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Senior IT System EngineerIT ProfessionalAsked:
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Jian An LimSolutions ArchitectCommented:
wow. you make a lot of bold statement :)
there are definitely some downtime or issues to the end users but as a sales pitch it looks well.

let's work one by one.

statement 3 is partially correct. I won't say Office 365 won't have bug/issues, calendaring and delegate issues that normally seen in on-premise should not happen as the servers are more centrally managed.

Statement 4. You can still utilize journaling. Just a question, why bother with Symantec Enterprise Vault are more painful to manage? MIcrosoft has in-place hold (effectively replace journaling), or you still don't trust them, you can backup them seperately (3rd party company do so, like 3 dollars per user per month)
I will also highlight that since office 365 offers a 50GB mailbox (which is much bigger than your current environment), you don't need to worry about Archiving at onpremise. (if you are on E3 licences)

Statement 5, over business hours is just too hot, i will not say that without doing any analysis on your network performance. Usually, i will do it when the network utilisation is low.

Statement 6 is like sales pitch. :)

For manager purpose, they are always looking at cost.
you need to explain CAPEX and on-going OPEX involved.
Also you need to explain about RTO and RPO. and the risk of going ahead.

There are a lot of moving parts because the solution you are putting in involve ADFS/Hybrid Exchange/etc
Senior IT System EngineerIT ProfessionalAuthor Commented:

Thanks for the reply, regarding ADFS/Hybrid Exchange deployment, no there is no hybrid AD or ADFS, my plan is to:

Migrate all Exchange mailboxes to Office 365 so that I can fully decommission all Exchange Servers, therefore all user Outlook will just directly repoint to the cloud IP address for all users globally.

Do I still need exchange servers in house / on-premise ? Because the idea of moving the email to the cloud is for reliability feature where there is disaster strikes the head office, my company can still be working as long as there is internet connection to the Office365.com website.

I do not plan to move / migrate the existing domain controllers to the cloud.
Jian An LimSolutions ArchitectCommented:
you are talking about 5000 seats (and imagine, you also have shared mailbox and etc) here.
there will be hybrid Exchange environment for sure.
you can't move everything over a night. and you don't want to do a cutover as you will definitely kill it.

a full hybrid environment is recommended. the first exchange 2013 hybrid licence is free (no mailbox allowed)

for identity, if you don't want adfs, then at least you want to a synchronized identity. So you will require to install at least a Dirsync (or AADSync or AADConnect) server to replicate the directory to Office 365.

further, think about any application/tools that require to send emails. most of the fax and etc is not office 365 friendly, or they cannot authenticate themselves. Then you will need to keep at least 1 exchange server in-house until you get rib of them.
There are a lot more business case to think there are required.

I will recommend you seek out a Microsoft partner to help you to develop your plan or get their experts to assist you after you secure your funding :)
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Senior IT System EngineerIT ProfessionalAuthor Commented:
Ah I see,

So by using the Office 365, I will still require to deploy Exchange Server 2013/2016 non Mailbox role just to redirect the SMTP email traffic ? is that correct ?

Yes, so does this means also the hardware load balancer that is now in use for HT-CAS traffic will not be required anymore ?
Jian An LimSolutions ArchitectCommented:
that is during hybrid situation, you can decide to keep or drop at later stage.

Imagine, you have 13TB+ email to transfer out from your in-house to internet. This could not be done within 1 month, if not your Internet bill will be very "ugly" OR your network team will not be happy.

hardware load balancer will not be required at the end of the day, but during that, there are lot of coexistence and hybrid need to be configured.
Senior IT System EngineerIT ProfessionalAuthor Commented:
Ok, thanks man,
so how about the first two assumption or statements :-)

1. For High Availability, all mailboxes migrated to Office 365 will not require the Internal IT Staff to create or worry about DAG it will always be online with high availability in all different continent.

2. No need to worry about Windows Update to the Exchange Servers as this is fully transparent to the users and internal IT staff

is that achievable ?
Jian An LimSolutions ArchitectCommented:
there are not wrong.

depends on how you look at it. High availability is correct subject to Office 365 SLA (if it is down, it is down, you just need to pull out the call to microsoft or wait)

office 365 patching is according to microsoft schedule. user still need to update their windows/outlook and etc.

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