SMTP hang every 1 week from Spam attack

[Carlos]

Hi,

We used the standard SMTP services come with Win2K server act as the mail
relay gateway.
I don't understand why this server hang almost every week and almost every
Sun.
I realised that we have a heavy "spam" on SUN where we receied 500K++ emails
in 1 day.
I have no idea to block these spammers, I believe it is a "direct" attack.
It send all kind of NDR spams such as (e-mail address removed), (e-mail address removed),
(e-mail address removed) where the domain is mycompany domain and the recipient is
invalid. Even I can create a rule in our mail filtering software to filter
these emails, these 500K+++ emails still process by the SMTP service and I'm
not sure because of this reason the SMTP service hang.
I reboot the server and everything is fine. I have already configured the
SMTP to receive 250 connections simultaneously already, however, the spammer
is still able to crash the SMTP service.

Are you guys experiencing this too ?

Please help.

Thanks

 

[William Yuen]

I have encounter same problem 1 weeks ago with my IIS4 SMTP server as
gateway.

I fixed it by disable "allow authenicated user to relay" function in SMTP
server property.

Hope this work for you. Also check the SMTP log.

William

 

[GHalleck]

I have encounter same problem 1 weeks ago with my IIS4 SMTP server as
gateway.

I fixed it by disable "allow authenicated user to relay" function in SMTP
server property.

Hope this work for you. Also check the SMTP log.

William

<<snipped>>

By doing this, doesn't it really mean that the trojan still exists on a system that
is somewhere on the LAN? That is, the source of the problem still persists.