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SMTP filter - 12.Mar.2002 3:28:00 PM

Abuislam

Posts: 7
Joined: 12.Mar.2002
From: NY
Status: offline

Hi Tom-
When I am enabling SMTP filter, I am getting following 2 errors is ISA server's eventlog. Some of my clients reported that their emails bounced back from my Exchange server 5.5 SP4. Any help to resolve this will be highly appreciated. Thanks.
Bye the way- I bought your book and I think it is the best book for ISA server.

Error 1:
Source:SmtpEvt, Event ID: 20033
The SMTP command exceeded its allowed length.
0000: 4e 4f 4f 50 20 20 20 20 NOOP

Error 2:
Source:SmtpEvt, Event ID: 20031
An unknown SMTP command
0000: 58 45 58 43 48 35 30 20 XEXCH50

Post #: 1

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RE: SMTP filter - 13.Mar.2002 2:57:00 PM

Abuislam

Posts: 7
Joined: 12.Mar.2002
From: NY
Status: offline

Hi Tom-
My Exchange 5.5 SP4 server is behind the ISA server. I have installed SP1 [latest one] on ISA. I haven't installed Message Screener service yet. I was keep getting SMTP filter errors. So, I have increased the maximum length of NOOP SMTP command to 24 bytes from 6 bytes. Now I am not getting the following error:
Source:SmtpEvt, Event ID: 20033
The SMTP command exceeded its allowed length.
0000: 4e 4f 4f 50 20 20 20 20 NOOP
Is it safe to do this? I have checked SMTP RFC2821. It does not say what should be the maximum length of NOOP command.
However I am still getting following error:
Source:SmtpEvt, Event ID: 20031
An unknown SMTP command
0000: 58 45 58 43 48 35 30 20 XEXCH50
I didn't find any SMTP command called XEXCH50 in RFC2821.
Help! Thanks.

(in reply to Abuislam)

Post #: 2

RE: SMTP filter - 16.Mar.2002 6:19:00 PM

tshinder

Posts: 47659
Joined: 10.Jan.2001
From: Texas
Status: offline

Hi Raju,

Its OK to drop NOOP requests, since they don't provide any needed functionality. The EXCH50 indicates that another Exchange Server is sending to you. You can add a EXCH50 entry, but I don't know the length of the command. Therefore, I prefer not to allow it, since if I don't know the proper length, putting in an arbitrary value could open me up to a buffer overflow.

HTH,
Tom

(in reply to Abuislam)

Post #: 3