<div>
This should clear all your doubt<br />
<a href="http://channel9.msdn.com/Series/Migrating-to-Exchange-Online/01" rel="ugc">http://channel9.msdn.com/Series/Migrating-to-Exchange-Online/01</a>
</div>


This should clear all your doubt
http://channel9.msdn.com/Series/Migrating-to-Exchange-Online/01 [http://channel9.msdn.com/Series/Migrating-to-Exchange-Online/01]

<div>
Few more things<br />
- since there are two HT servers, and we have NLB appliance, we can publish to the NLB cluster IP?<br />
- should we run HCW on both HT servers or running HCW on only one &nbsp;server will configure whole environment for high availability ?
</div>


Few more things
- since there are two HT servers, and we have NLB appliance, we can publish to the NLB cluster IP?
- should we run HCW on both HT servers or running HCW on only one  server will configure whole environment for high availability ?

<div>
<div class="content wysiwyg-content">
Current configuration : &nbsp;multiple hub transport servers, multiple CAS servers, third party messaging gateway<br />
Dirsync is already in place for other functions<br />
wildcard certificate exists<br />
i didn't yet completed or tried HCW<br />
1. after HCW mail flow for on-premise users will stay the same ?<br />
2. do we need to publish all hub transport servers to internet/port 25 ?<br />
3. what IP adreses does hub transport communicates with, what ip addreseses i need in firewall rule , these <a href="https://technet.microsoft.com/en-us/library/dn163583%28v=exchg.150%29.aspx" rel="ugc nofollow">https://technet.microsoft.com/en-us/library/dn163583%28v=exchg.150%29.aspx</a>&nbsp;?<br />
4. i was thinking first leave MX record as is pointing to SMTP messaging appliance and after we are clear that everything is ok , point it to EOP ?
</div>
</div>


Current configuration :  multiple hub transport servers, multiple CAS servers, third party messaging gateway
Dirsync is already in place for other functions
wildcard certificate exists
i didn't yet completed or tried HCW
1. after HCW mail flow for on-premise users will stay the same ?
2. do we need to publish all hub transport servers to internet/port 25 ?
3. what IP adreses does hub transport communicates with, what ip addreseses i need in firewall rule , these https://technet.microsoft.com/en-us/library/dn163583%28v=exchg.150%29.aspx ?
4. i was thinking first leave MX record as is pointing to SMTP messaging appliance and after we are clear that everything is ok , point it to EOP ?

Exchange 2010 SP3 Hybrid configuration

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Exchange

Office 365 is a group of software plus services subscriptions that provides productivity software and related services to its subscribers. Office 365 allows the use of Microsoft Office apps on Windows and OS X, provides storage space on Microsoft's cloud storage service OneDrive, and grants 60 Skype minutes per month. Office 365 includes e-mail and social networking services through hosted versions of Exchange Server, Skype for Business Server, SharePoint and Office Online, integration with Yammer, as well as access to the Office software. All of Office 365's components can be managed and configured through an online portal; users can be added manually, imported from a CSV file, or Office 365 can be set up for single sign-on with a local Active Directory using Active Directory Federation Services.

Microsoft 365

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.