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mail relay vs smtp

Posted on 2011-02-16
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Last Modified: 2012-05-11
there is outgoing mail, but there is no service called smtp. the admin says mail relay is happening. what exactly does this mean?

thanks
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Question by:anushahanna
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by:scriven_j
ID: 34908618
The service is actually called Simple Mail Transfer Protocol.....
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by:anushahanna
ID: 34908635
i do not see "Simple Mail Transfer Protocol" in services.msc
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by:scriven_j
ID: 34908637
Mail Relay means that the mail is being passed from your Exchange Server to the next server down the line.
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by:reijer
reijer earned 50 total points
ID: 34908671
If its an Smal business server 2008, wiyh exchange 2007 server. Mailrelay is handled by the exchange server. You can go to the management console or gui to view the hub settings
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by:scriven_j
ID: 34908676
Open a command prompt and type

net start smtpsvc

Open in new window


Let us know what happens....
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by:scriven_j
ID: 34908686
Yes, probably should have clarified OS / Exchange version etc!
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by:scriven_j
ID: 34908698
I use Exchange 2003 and so assumed! :S
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by:scriven_j
ID: 34908726
This might be helpful if is is Exchange 2007 (or 2010)

http://technet.microsoft.com/en-us/library/aa998662.aspx
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by:Hypercat (Deb)
Hypercat (Deb) earned 50 total points
ID: 34908831
For Exchange 2007, the service is called "Microsoft Exchange Transport."  This is the service that controls SMTP communication.  Why do you need to know this if you aren't the administrator of the system? Who is the "admin" that says mail relay is happening?
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by:anushahanna
ID: 34909350
>>Mail Relay means that the mail is being passed from your Exchange Server to the next server down the line.

so this does not have to have a service running?

In this particular machine, it is OS 2003 with exchange 2003.

So, in mail relay the same or different than SMTP?
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by:anushahanna
ID: 34909427
C:\Documents and Settings\jimwe>net start smtpsvc
The service name is invalid.

More help is available by typing NET HELPMSG 2185.


C:\Documents and Settings\jimwe>
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by:Amit
Amit earned 50 total points
ID: 34909482
What's a "Relay"?
First let's see what "relaying" is:

A user in your domain wants to send e-mail to another user in your domain - This is NOT relaying.

An outside user (from the Internet) wants to send e-mail to another user in your domain - This is NOT relaying.

A user in your domain wants to send e-mail to an outside user (on the Internet) - This IS relaying.

An outside user (from the Internet) wants to send e-mail to an outside user (on the Internet) - This IS relaying.

The default Exchange 2000/2003 configuration does not allow unauthenticated users to relay through the server.

http://www.petri.co.il/preventing_exchange_2000_2003_from_relaying.htm

Secondly, check the tracking logs from where it is passing.
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by:Hypercat (Deb)
ID: 34909746
Whether you are relaying mail or not, if there's no SMTP service running on the server, then Exchange isn't properly installed and cannot be working properly. Is it possible that the users in this company are sending mail using POP3 from their Outlook client without actually using an Exchange mailbox at all?
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by:anushahanna
ID: 34909817
OK- sorry I did not ask the question more clearer..

there is outgoing mail (from the client box), but there is no service called smtp (in the client box). the admin says mail relay is happening, (and the client box will still be able to send emails out to the world). what exactly does this mean?

from what you are saying, it seems port 25 needs only be opened on the exchange server.

so, through what port is the client box able to send out emails?
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by:anushahanna
ID: 34909831
i am only touching the client box and not the exchange box.
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by:scriven_j
ID: 34909908
OK - well Small Business Server 2003 Exchange can be configured to use POP3, so this is probably how you have things configured.

http://www.msexchange.org/tutorials/Configuring-Incoming-Outgoing-Email-Windows-Small-Business-Server-2003.html
http://support.microsoft.com/kb/885685

I thought it still used SMTP to send outbound mail, but I might be wrong.  Either way you can look at the Connectors in System Manager (as outlined in figure 20 of the first link) and see.  If you are still confused, then take a screenshot of that and post it here.
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by:scriven_j
ID: 34909919
OK - sorry - my post crossed.

Outlook connects to the Exchange server and it is only Exchange that needs SMTP.
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by:scriven_j
ID: 34909934
Port 25 only needs to be open on Exchange if it is receiving maiol from external servers (if you are using POP3 only, then this wouldn't be the case).  Can't your admin give you the information you need?
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by:scriven_j
ID: 34909975
Internally Outlook and Exchange communicate using RDP.

http://support.microsoft.com/kb/833799/
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by:scriven_j
ID: 34909984
Why don't you tell us why you are asking these questions?  Then we might be able to give you clearer answers!
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by:anushahanna
ID: 34910032
scriven_j, i was mistaken that the client machine should have port 25 open to send email. i believe i am wrong, after reading your posts.

i did 'telnet ipaddressofexchange 25' and it worked.

so in the above context, trying to understand 'mail relay', is just that the client machine is consider "in the world" and hence mail relay is happening, by post # 34909482

when the client machine is sending out an email, what port would it be using to send it out?
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by:scriven_j
ID: 34910233
When you connect to an open port, the machine that is connecting will just open a random port for the response.  It is not really important and even a firewall should not block it, as it has been initiated from behind the firewall.

Your telnet command is connecting to Exchange in the same way as an external email server would do to relay mail items to your Exchange server, via Port 25, however RDP (which Outlook would use to communicate with Exchange) uses Port 135.

If you want to see what port your client is using, open a command window and type:-

netstat -na

Open in new window


This will show all the connections to ports (outbound and inbound).

Hope this is all clear?
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by:scriven_j
ID: 34910251
If the output of Netstat is confusing, download and run TCPView and it should make things a bit clearer.

http://technet.microsoft.com/en-gb/sysinternals/bb897437

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by:anushahanna
ID: 34910375
thanks - using tcpview on a client machine, i see outlook using 3000? here are sample 4 rows

Outlook.exe:3000    machinename:2383      exchangeserver1:5002           ESTABLISHED
Outlook.exe:3000    machinename:2381      exchangeserver2:5002           ESTABLISHED
Outlook.exe:3000    machinename:2377      exchangeserver3:5002           ESTABLISHED
Outlook.exe:3000    machinename:1121      exchangeserver4:1026           ESTABLISHED

how would you interpret this?
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scriven_j earned 350 total points
ID: 34910393
Just to clarify the process in case you are not clear....

1. Your Outlook (client) connects to Exchange (server) via RPC (Remote Procedure Call) using Port 135
2. When you send a mail Exchange looks at whether it is internal (someone else that the Exchange server handles mail for) or external.

If it is internal, then it routes the mail to the new mailbox, but it doesn't leave the server.

If it is external, then Exchange will connect to the mail server responsible for the domain that you are Emailing (as stated in the DNS MX record.  It connects using Port 25 on the receiving mail server and communicates using the SMTP protocol).

3. When someone replies, the process is reversed.  So communication to your server on Port 25 only takes place when mail is being sent TO your mail server.



3. When mail is coming in,
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by:scriven_j
ID: 34910474
I think the port numbers are the numbers after the machinename and the exchangeserver.

Once the machines are connected, they can change ports and this is normal (as you can see the machinename stepped up the sequence 2377, 2381, 2383 and will keep changing).

I don't see anything to be concerned about in what you have posted though.....
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by:anushahanna
ID: 34910482
OK- i am getting it - If it is external address which outlook is sending email, then it is mail relay

why could i not see port 135 in TCPView? and what are the 3000/2383/5002 ports?
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by:anushahanna
ID: 34910488
>>Once the machines are connected, they can change ports
so, originally it is 135 and then it can change?
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by:scriven_j
ID: 34910500
In fact I think Outlook Anywhere uses ports 5000 - 5004.  Not sure about 1026, but I am not worried by what you have posted.
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by:scriven_j
ID: 34910512
I am not an expert on Ports, but yes, they can change once the connection is established.
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by:anushahanna
ID: 34910527
Thanks for all the helpful answers.. appreciate it.
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by:scriven_j
ID: 34910554
Looks like your Exchange server has been configured to use Static Ports

http://objectmix.com/microsoft-exchange/278295-set-static-port-mappings-exchange-2003-server%3B-now-vpn-clients-cannot-use-outlook-xp-offsite.html

Exchange Information Store Interface Port = 5002
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by:scriven_j
ID: 34910585
Apparently 1026 is the Calendar Access Protocol, so sounds like Outlook too!
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