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Where does email go when using SMTP service?

I have a Windows 2000 server between my cable modem and my network switch.  It acts as firewall and DHCP server.  My question is regarding the SMTP service that is running on the server.  I do NOT have Exchange, so the native SMTP service is all I have in regards to email capabilities on this server.  You are aware that the administrator can send out email by using Notepad, and creating a text file and saving it in folder C:\Inetpub\mailroot\Pickup ?  The format of the text file would be:

----------------------------------------------------------------------
TO: sysadmin@anywhere.com
FROM: whatever@here.com
SUBJECT: Automated message

Place your text here

----------------------------------------------------------------------

I have 2 questions related to this:

1) Having the SMTP service running on this server, do I expose my server to SPAMmers who might use this SMTP service to relay mail through?  If 'yes', what can I do (short of ending the SMTP service) to prevent this?

2) If I were to drop one of these text files into the \pickup folder, and the recipient's email address was invalid, or the domain portion was no longer active, what would happen to the email?  IOW, let's say I had the 'TO:' parameter set to...

TO: bill_gates@microsoft.com
FROM: whatever@here.com

Where would this email end up, knowing in advance that bill_gates@microsoft.com is an invalid email?

And what if the email was sent to:

TO: bill_gates@this_is_the_time_for_all_good_men_to_come_to_the_aid_of_their_country.com

???

Where would this email end up?  Would bounced emails be returned to the email address designated in the "FROM:" field?  And what if this "FROM:" field was bogus?

Obviously there is no POP service running on this Windows 2000 server, so where would these bounced emails get bounced back to?
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Monroe406
Asked:
Monroe406
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1 Solution
 
AvonWyssCommented:
1. You can limit the relaying in the properties of the service. Or you can even make that the SMTP server is not bound to the interface on the cable, so that in fact the SMTP server would not be reachable over the cable connection but onlya locally and over the LAN. This would of course be the best solution.

2. The server will process the mail just as if it had received it by SMTP. This means that first it will try to connect to that remote domain. Then, when it notices that the mailbox is invalid or that the domain cannot be reached (the latter case will be retried a couple of times), the SMTP server will generate a NDR (Non-Delivery Report) and try to send it to the sender address. If this fails also, the mail will be put into the BADMAIL directory.
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Monroe406Author Commented:
>> Or you can even make that the SMTP server
is not bound to the interface on the cable, so that in fact the SMTP server would not be reachable over
the cable connection but onlya locally and over the LAN. <<

How do you do that?
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AvonWyssCommented:
In case you have not yet found this out yourself, it's in the properties of the SMTP site, where you can specify what addresses it should be active on.
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Monroe406Author Commented:
>>it's in the properties of the SMTP site<<

SMTP site?  I'm not sure I follow?  Could you be more specific?  START > PROGRAMS > ????  >  ????
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