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date: Fri, 7 Apr 2006 13:00:11 +0200,
group: microsoft.public.exchange.tools
back
Re: Telnet and Exchange
In news:OK7qfyBXGHA.196@TK2MSFTNGP04.phx.gbl,
Nicolas Macarez typed:
> Thanks for all your answers....
>
> In fact, what I want to do is to prevent anyone from the Internet
> using my Exchange Server to send (open relay?) e-mails without any
> need to authenticate himself, by using telnet commands on the port 25.
I think you're still missing something here; you're looking at this
backwards. Relay isn't about a telnet connection....relay is about your
server allowing someone to send mail *through*, not *to* your server.
E2003 is not an open relay by default, and you can easily stop even
authenticated relay - in fact, if you performed the steps you mention below,
you already did.
See http://www.msexchange.org/tutorials/MF005.html for a good overview of
relaying and spam.
>
> I checked to be sure that my Exchange server is not an open relay :
>
> Under the Exchange System Manager :
> First Organization (Exchange)
> Administrative Groups
> First administrative group
> Servers
> <MACHINE_NAME>
> Protocols
> SMTP
> Default SMTP Virtual Server
> right-click and then Properties
> Access tab
> Relay button in Relay Restrictions
> Only the list below is checked (and the list is empty)
>
> Is there any real threat or do I need to set something special in the
> firewall (we are expecting a CISCO 1841 box soon...)
>
> Help appreciated
> Nicolas
>
>
>
> "Rob Godfrey" wrote in message
> news:%23FXFH$$WGHA.1204@TK2MSFTNGP04.phx.gbl...
>> That would prevent all incoming mail NOT prevent telnet (actually
>> just an SMTP command prompt not telnet).
>>
>> What you're seeing when you 'telnet' to port 25 is the Exchange side
>> of an SMTP 'conversation'. Instead of another SMTP server the
>> connection has been initiated by a person at a command prompt. The
>> Exchange server HAS to be able to respond to requests to initiate
>> SMTP 'conversations' in order to receive incoming email. This is
>> quite normal and is not telnet.
>>
>>
>> "." <noemails@please> wrote in message
>> news:OvpUetnWGHA.3800@TK2MSFTNGP03.phx.gbl...
>>> Email coming to your company is accepted by an open port 25. If
>>> port 25 is not open on some email server, your company cannot get
>>> any inbound email.
>>>
>>> If you don't want this, use your firewall to stop it.
>>>
>>> Ray
>>>
>>>> "Nicolas Macarez" wrote in message
>>>> news:eRaVrJjWGHA.1564@TK2MSFTNGP03.phx.gbl...
>>>>> Hi!
>>>>>
>>>>> I wish to prevent any access by Telnet on port 25 from the
>>>>> outside of my organization.
>>>>>
>>>>> I am running W2K3 Server, with Exchange 2003 Server installed.
>>>>>
>>>>> The telnet service is disabled in the Windows Server, but I can
>>>>> still telnet
>>>>> and get the Microsoft exchange banner on port 25 from he Internet.
>>>>>
>>>>> Any idea?
>>>>>
>>>>> Help appreciated.
>>>>>
>>>>> Nicolas
date: Sun, 9 Apr 2006 21:44:23 -0400
author: Lanwench [MVP - Exchange]
Re: Telnet and Exchange
In news:u7fqjCEXGHA.4924@TK2MSFTNGP05.phx.gbl,
Lanwench [MVP - Exchange]
typed:
> In news:OK7qfyBXGHA.196@TK2MSFTNGP04.phx.gbl,
> Nicolas Macarez typed:
>> Thanks for all your answers....
>>
>> In fact, what I want to do is to prevent anyone from the Internet
>> using my Exchange Server to send (open relay?) e-mails without any
>> need to authenticate himself, by using telnet commands on the port
>> 25.
>
> I think you're still missing something here; you're looking at this
> backwards. Relay isn't about a telnet connection....relay is about
> your server allowing someone to send mail *through*, not *to* your
> server.
> E2003 is not an open relay by default, and you can easily stop even
> authenticated relay - in fact, if you performed the steps you mention
> below, you already did.
Oops, you didn't mention the checkbox for "allow all users who successfully
authenticate...", which is what I mean.
>
> See http://www.msexchange.org/tutorials/MF005.html for a good
> overview of relaying and spam.
>
>
>>
>> I checked to be sure that my Exchange server is not an open relay :
>>
>> Under the Exchange System Manager :
>> First Organization (Exchange)
>> Administrative Groups
>> First administrative group
>> Servers
>> <MACHINE_NAME>
>> Protocols
>> SMTP
>> Default SMTP Virtual Server
>> right-click and then Properties
>> Access tab
>> Relay button in Relay Restrictions
>> Only the list below is checked (and the list is empty)
>>
>> Is there any real threat or do I need to set something special in the
>> firewall (we are expecting a CISCO 1841 box soon...)
>>
>> Help appreciated
>> Nicolas
>>
>>
>>
>> "Rob Godfrey" wrote in message
>> news:%23FXFH$$WGHA.1204@TK2MSFTNGP04.phx.gbl...
>>> That would prevent all incoming mail NOT prevent telnet (actually
>>> just an SMTP command prompt not telnet).
>>>
>>> What you're seeing when you 'telnet' to port 25 is the Exchange side
>>> of an SMTP 'conversation'. Instead of another SMTP server the
>>> connection has been initiated by a person at a command prompt. The
>>> Exchange server HAS to be able to respond to requests to initiate
>>> SMTP 'conversations' in order to receive incoming email. This is
>>> quite normal and is not telnet.
>>>
>>>
>>> "." <noemails@please> wrote in message
>>> news:OvpUetnWGHA.3800@TK2MSFTNGP03.phx.gbl...
>>>> Email coming to your company is accepted by an open port 25. If
>>>> port 25 is not open on some email server, your company cannot get
>>>> any inbound email.
>>>>
>>>> If you don't want this, use your firewall to stop it.
>>>>
>>>> Ray
>>>>
>>>>> "Nicolas Macarez" wrote in message
>>>>> news:eRaVrJjWGHA.1564@TK2MSFTNGP03.phx.gbl...
>>>>>> Hi!
>>>>>>
>>>>>> I wish to prevent any access by Telnet on port 25 from the
>>>>>> outside of my organization.
>>>>>>
>>>>>> I am running W2K3 Server, with Exchange 2003 Server installed.
>>>>>>
>>>>>> The telnet service is disabled in the Windows Server, but I can
>>>>>> still telnet
>>>>>> and get the Microsoft exchange banner on port 25 from he
>>>>>> Internet. Any idea?
>>>>>>
>>>>>> Help appreciated.
>>>>>>
>>>>>> Nicolas
date: Sun, 9 Apr 2006 22:54:33 -0400
author: Lanwench [MVP - Exchange]
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