Exchange Mail route

I might have asked this question  in  the past but want more confirmation.
The flow of email in Exchange 2003/2007 & 2010

in Exchange 2003

Internal mail:
Reading email from exchange server: Outlook connects to Exchange server and reads email
when sending from  internal to external, it goes straight to internet without going through Front End server
External email : if it's coming through OWA, outlook mobile phone, blackberry ( user has an account in the exchange server), then it should go through Front end server to back end server.
                            if it s coming from public emails such as Hotmail or Yahoo then it goes straight to exchange server without going through front end server.

BUT , I have seen environments that don't have Front End Exchange server , just the Back End-- so what is the pros and cons of having FE or not having it.


in Exhcange 2007 & Exchange 2010

Internal email : when viewing email , Outlook connects to Exchange Mailbox server role and view the emails without going through Client Access .
                           when sending internal email to internal email address, outlook sends an email straight to Exchange Mailbox role server without going through Client Access role

when sending internal email to external email, the email goes from the Mailbox to the HUB and to the EDGE then to internet, [without passing through Client Acces]

External  email: if it 's sent through OWA, outlook mobile phone, blackberry ( user has an account in the exchange server) the email comes through EDGE to HUB to Client Access server then to  Mailbox server.
                           if it's sent through Yahoo, Hotmail then it comes through EDGE to HUB to Mailbox server without passing through Client Access.

***CLIENT ACCESS ROLE is kind of confusing , any Exchange2007/2010 expert to clear this confusion up?

Thanks
jskfanAsked:
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AkhaterCommented:
Internal mail:
Reading email from exchange server: Outlook connects to Exchange server and reads email
when sending from  internal to external, it goes straight to internet without going through Front End server
External email : if it's coming through OWA, outlook mobile phone, blackberry ( user has an account in the exchange server), then it should go through Front end server to back end server.
                            if it s coming from public emails such as Hotmail or Yahoo then it goes straight to exchange server without going through front end server.

BUT , I have seen environments that don't have Front End Exchange server , just the Back End-- so what is the pros and cons of having FE or not having it.

This is wrong you do not need FE for mail flow, actually FE has nothing to do with mail flow (it could have but not necessary) the purpose of the FE is for client access like OWA, RPC/HTTP, POP3 IMAP, activesync when you have more than one mailbox server

Exchange 2007:
Outlook will connect directly to the MAILBOX server, emails routing happens on the HUB server
CAS has nothing to do with email routing it is just an interface to see or connect to to the mailbox when using clients like OWA, RPC/HTTP, POP3 IMAP, activesync

Exchange 2010:
emails routing happens on the HUB server
CAS has nothing to do with email routing it is just an interface to see or connect to to the mailbox when using clients like OWA, RPC/HTTP, POP3 IMAP, activesync and OUTLOOK (different from exchange 2007 in the outlook part)
Mailbox just holds he mailboxes

hope it helps
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jskfanAuthor Commented:
<<<This is wrong you do not need FE for mail flow, actually FE has nothing to do with mail flow (it could have but not necessary) the purpose of the FE is for client access like OWA, RPC/HTTP, POP3 IMAP, activesync when you have more than one mailbox server>>>

Correct if I am not understanding it

Correct if I am not understanding it

Exchange 2003
I have seen an environment where they have only one Exchange server and they have FE.
it is used for the external emails that come from users that already have mailboxes on the exchange server for instance OWA users, not from hotmail or yahoo emails that are sent  straight to the exchange server.

Exchange 2007/2010

If I understand you are saying CAS is used only for internal users to read emails from Mailbox server,
when internal users send emails to other internal users does it go through CAS? I guess you are saying NO. Correct?
When internal users send emails to external users does it go through CAS?I guess you are saying NO. Correct?

When users opens OWA from Home and login successfuly  to read their emails, are they going through CAS? and what about when they send email from OWA , is the email going through CAS which I believe it is not.

emails that come from hotmail or yahoo are sent straight to mailbox server via EDGE and  Hub , they don't go through CAS. Correct?
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AkhaterCommented:
>>>I have seen an environment where they have only one Exchange server and they have FE.

Yes it can exist but it is useless again FE has nothing to to with mail routing and it is redundant if you have only 1 mailbox serer


>>xchange 2007/2010

If I understand you are saying CAS is used only for internal users to read emails from Mailbox server,
when internal users send emails to other internal users does it go through CAS? I guess you are saying NO. Correct?
When internal users send emails to external users does it go through CAS?I guess you are saying NO. Correct?<<

NO Not correct, in exchange 2007 CAS is NOT used for internal users if they are using outlook it will connect directly to maiblox server. CAS is for OWA, RPC/HTTP, IMAP/POP3 and Activesync

in exchange 2010 CAS is for ALL clients

emails does NOT go thru CAS, CAS is just an interface



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jskfanAuthor Commented:
I also don't understand why some environments use Load balancing for CAS, if it's only used as an interface to read mail.
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AkhaterCommented:
>>emails that come from hotmail or yahoo are sent straight to mailbox server via EDGE and  Hub , they don't go through CAS. Correct?<<

no email will go thru the CAS, the CAS is an interface

internal email will be something like

Mailbox -> HUB -> Mailbox

external

Mailbox -> HUB -> Edge -> Internet
Internet -> Edge -> Hub -> Mailbox
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jskfanAuthor Commented:
Sending and reading should be different.
if sending emails doesn't go through CAS, what about reading ?
 which type clients that go through CAS when reading email?
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AkhaterCommented:
no email goes through CAS, again CAS is an interface

once more


 in exchange 2007 CAS is NOT used for internal users if they are using outlook it will connect directly to maiblox server. CAS is for OWA, RPC/HTTP, IMAP/POP3 and Activesync
Outlook connects directly to the mailbox server


in exchange 2010 CAS is for ALL clients, all clients will connect to cas to retreive their emails
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jskfanAuthor Commented:
<<in exchange 2010 CAS is for ALL clients, all clients will connect to cas to retreive their emails>>
Thanks , I was looking for that.
So all clients when they view their emails they go through EDGE->HUB-->CAS-->Mailbox
and all clients when they send emails they go through EDGE-HUB-->Mailbox

 public emails such as Hotmail can send email and it will go through EDGE-->HUB-->Mailbox


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AkhaterCommented:
So all clients when they view their emails they go through EDGE->HUB-->CAS-->Mailbox
and all clients when they send emails they go through EDGE-HUB-->Mailbox

 public emails such as Hotmail can send email and it will go through EDGE-->HUB-->Mailbox

NO


Email flow is
Internal email will be something like

Mailbox -> HUB -> Mailbox

external

Mailbox -> HUB -> Edge -> Internet
Internet -> Edge -> Hub -> Mailbox


TO VIEW the email it is

Client <-> CAS <-> Mailbox
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jskfanAuthor Commented:
Thanks, one thing missing,
if you want to view email using  OWA, and you are :
1- in public place using OWA
2 -you are inside the LAN but using OWA.
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AkhaterCommented:
when you use owa you always use the CAS no matter if it is from lan or public
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jskfanAuthor Commented:
Excellent
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