Open relay

Avast Free Antivirus / Premium Security
1

If i install avast MSTP feature, my computer become open relay. How to change settings?

I want accept messages on port 25 because I run small mail server on my computer.

2

avast! SMTP feature? Do you mean turning on the scanning of outbound e-mail (in avast! Home/Pro), or are you talking about avast! Server Edition maybe?

3

Jup, I mean turning on the scanning of outbound e-mail. As far as I noticed, they also accept connections from outside. Because I don’t want to set trusted IPs.

4

It certainly should not accept connections from outside - only from the local host!
Are you sure abou it? How did you test?

5

Ups.
I tested with some thirdparty openrelay script/site. How I see, they was comunicateing with avast. I will test once again.

Does avas do same caching on SMTP connection?

6

What catching ?
Avast mail scanner works as a proxy on winsock level, it does no low-level operations with connections.

7

Ok, I connect directly on port 25 with telnet and do some tests. Avast! changeing reply from smtp server, and that make me comfused.

via avast:

220 X2003 avast! SMTP proxy ready.
helo nastja.com
250 X2003
mail from:marko@nastja.com
501 5.5.4 Invalid Address
mail from:marko@nastja.com
250 2.1.0 marko@nastja.com…Sender OK
rcpt to:marko@nastja.com
250 2.1.5 marko@nastja.com
data
354 Enter mail, end with “.” on a line by itself
test
.
250 2.6.0 KNEZFlz43dWI5KBTl2X00000bdc@smtp.b2-ic.si Queued mail for delivery

without avast:
220 smtp.b2-ic.si Microsoft ESMTP MAIL Service, Version: 6.0.3790.0 ready at Mo
n, 9 Feb 2004 14:03:30 +0100
helo nastja.com
250 smtp.b2-ic.si Hello [194.165.105.7]
mail from:marko@nastja.com
250 2.1.0 marko@nastja.com…Sender OK
rcpt to:marko@nastja.com
d250 2.1.5 marko@nastja.com
ata
354 Start mail input; end with .
dtest

.
250 2.6.0 KNEZHv1cO9MH7CSEI5W00000be2@smtp.b2-ic.si Queued mail for delivery

8

If you have a SMTP server on port 25, you have to change the port for avast - insert such a line to the file Avast4\DATA\avast4.ini under [MailScanner]:
SmtpListen=127.0.0.1:26

Then you need to reconfigure accounts in your mail program, if you want to send through avast mail scanner.

9

Ej, IT works! SMTP server is not on same IP as avast!.

Is my diagnose that Avast change SMTP server response correct or not?

10

Yes, it is also an option.

Yes, it may use another response than your server, when it has to send the response before it receives corresponding response from the server.