Hello I'm trying to find out more information about IMAP and Exchange 2007 in terms of how mails are sent/recvd, but there doesn't seem to be much info. Currently, we are running Exchange 2003. We also use IMAP clients for a few people. Let's say we install a CAS and HT in a different AD site. We configure some of the existing IMAP clients to point to the CAS (since it's backwards compatible with Ex2003)? If an IMAP client sends an email, how does this work? I assume: Client > CAS: IMAP on port 143 But then I'm lost! Does the CAS server proxy the communication on port 143 to the Mailbox server that then sends the message to the nearest Hub Transport? Or does the CAS server itself send the message? And, for IMAP clients, does there have to be a IMAP enabled CAS in the same AD site? And how does this all work if the mailbox is on an Exchange 2007 mailbox server?

I think that the CAS server receives IMAP requests from IMAP clients and sends requests to the Mailbox server using RPC-MAPI. If an IMAP(also SMTP) client sends an email, this work as following: Client -> HT:SMTP on port 25 or 587 Copy of outgoing messages are created and saved to Sent Messages folder in the client. The Client sends an information that the client has saved outgoing messages to Send Messages folder using IMAP. The CAS server receive the information from the client and sends it to the Mailbox server using RPC-MAPI. The Mailbox Server receive the information from the CAS server and reflect it in the mailbox. Sorry,my english is not good.

On Thu, 4 Mar 2010 22:40:53 +0000, John 2188 wrote:>I'm trying to find out more information about IMAP and Exchange 2007 in terms of how mails are sent/recvd, but there doesn't seem to be much info. IMAP doesn't send messages so you can strike that from your search.:-)For the cross-site configuration stuff, see this: http://technet.microsoft.com/en-us/library/cc671173(EXCHG.80).aspx>>Currently, we are running Exchange 2003. We also use IMAP clients for a few people. >>Let's say we install a CAS and HT in a different AD site. Wait . . . the CAS and HT are in different AD sites, or the CAS is ina different AD site to the Mailbox server?>We configure some of the existing IMAP clients to point to the CAS (since it's backwards compatible with Ex2003)? It is. But there's nothing "backward". It's still IMAP.>If an IMAP client sends an email, how does this work? I assume: The e-mail is sent to whatever SMTP server the client is configured touse. IOW, it's probably set up to send the e-mail to one of your HubTransport servers.>Client > CAS: IMAP on port 143 >>But then I'm lost! >>Does the CAS server proxy the communication on port 143 to the Mailbox server that then sends the message to the nearest Hub Transport? No, the CAS proxies port 143 to the E2K3 mailbox server. No messagesare ever sent using IMAP. That's the job of the SMTP client that'spart of the IMAP e-mail client software.>Or does the CAS server itself send the message? >>And, for IMAP clients, does there have to be a IMAP enabled CAS in the same AD site? There does -- unless you follw the instructions in the link above.>And how does this all work if the mailbox is on an Exchange 2007 mailbox server? The CAS terminates the IMAP connection and uses MAPI/RPC to read themessage. Then it returns the message to the client.---Rich MatheisenMCSE+I, Exchange MVP--- Rich Matheisen MCSE+I, Exchange MVP

Excellent Rich, great answers.So, to confirm my understanding:Exchange 2003 mailbox:The MAPI client makes the connection to the CAS on 143. This is then proxied (still 143) to the E2k3 mailbox server.When sending a mail, the IMAP client submits the message to the Exchange 2003 Bridgehead/Exchange 2007 Hub Transport server.Messages *to* the mailbox are sent as any other message.Exchange 2007 mailbox:The MAPI client makes the connection to the CAS on 143. CAS then connects to the Mailbox server on MAPI/RPC.When sending a mail, the IMAP client submits the message to the Exchange 2003 Bridgehead/Exchange 2007 Hub Transport server.Messages *to* the mailbox are sent as any other message. Also, just some follow up questions: i) IMAP is only for recv'ing messages? It is a mail retrieval protocol or a mail client protocol would you say? ii) If there was a 2003 Mailbox server in SiteA, and a IMAP client in SiteA, does there need to be a CAS in SiteA as well, or will a CAS in SiteB suffice providing the bandidth is ok? iii) If there was a 2003 Mailbox server in SiteA, and a IMAP client in SiteA, does there need to be a Hub Transport in SiteA as well, or will a HT in SiteB suffice providing the bandidth is ok? iv) If there was a 2007 Mailbox server in SiteA, and a IMAP client in SiteA, does there need to be a CAS in SiteA as well, or will a CAS in SiteB suffice providing the bandidth is ok?v) If there was a 2007 Mailbox server in SiteA, and a IMAP client in SiteA, does there need to be a HT in SiteA as well, or will a HT in SiteB suffice providing the bandidth is ok?Thanks so much!

On Tue, 9 Mar 2010 14:18:10 +0000, John 2188 wrote:>>>Excellent Rich, great answers.So, to confirm my understanding:Exchange 2003 mailbox:The MAPI client makes the connection to the CAS on 143. This is then proxied (still 143) to the E2k3 mailbox server.When sending a mail, the IMAP client submits the message to the Exchange 2003 Bridgehead/Exchange 2007 Hub Transport server.Messages *to* the mailbox are sent as any other message.That's correct.>Exchange 2007 mailbox:The MAPI client Nope. The IMAP client does this.>makes the connection to the CAS on 143. CAS then connects to the Mailbox server on MAPI/RPC.Correct.>When sending a mail, the IMAP client submits the message to the Exchange 2003 Bridgehead/Exchange 2007 Hub Transport server.Messages *to* the mailbox are sent as any other message. Yes.>Also, just some follow up questions: >>i) IMAP is only for recv'ing messages? It is a mail retrieval protocol or a mail client protocol would you say? IMAP and POP are both mail retreival protocols. They're also mailclient protocols (but so is SMTP when it's sending e-mail).>ii) If there was a 2003 Mailbox server in SiteA, and a IMAP client in SiteA, does there need to be a CAS in SiteA as well, or will a CAS in SiteB suffice providing the bandidth is ok? I don't know how that would work with CAS and Exchange 2003. Exchange2003 didn't use AD sites, but Exchange 2007 does. But if you want ane-mail client to connect to an Exchange 2003 mailbox using IMAP, andthat e-mail client is on the LAN, you don't need a CAS at all -- justconnect to the mailbox server directly.>iii) If there was a 2003 Mailbox server in SiteA, and a IMAP client in SiteA, does there need to be a Hub Transport in SiteA as well, or will a HT in SiteB suffice providing the bandidth is ok? Any SMTP server will suffice, even the one on the Exchange 2003mailbox server.>iv) If there was a 2007 Mailbox server in SiteA, and a IMAP client in SiteA, does there need to be a CAS in SiteA as well, or will a CAS in SiteB suffice providing the bandidth is ok?This will work if you enable the cross-site proxying.>v) If there was a 2007 Mailbox server in SiteA, and a IMAP client in SiteA, does there need to be a HT in SiteA as well, or will a HT in SiteB suffice providing the bandidth is ok?You'll need a HT in every AD site where there's an Exchange 2007mailbox server. That's not dependant on any particular clientconnection.---Rich MatheisenMCSE+I, Exchange MVP--- Rich Matheisen MCSE+I, Exchange MVP