Following a server meltdown our new computer serving vamsoft.com was set up with Windows Server 2008 R2 (after running on 2003 for years). The installation itself went smoothly. The IIS 7 included in 2k8 is quite different from the previous version so I had to make a few adjustments – and learn a few new things -, but the real challenge begun when I started registering the smtp event sinks.

Started with the usual registering commands in a batch file, but the result was not familiar:

cscript smtpreg.vbs /add 1 onarrival NoreplyHandler CDO.SS_SMTPOnArrivalSink “rcpt to=noreply@*”
Microsoft (R) Windows Script Host Version 5.8
Copyright (C) Microsoft Corporation. All rights reserved.

Binding Display Name Specified: NoreplyHandler
** Registration Failed **
Err.Number (HRESULT) = 0x46
Err.Description = Permission denied
ProgID = CDO.SS_SMTPOnArrivalSink
COM Category = {FF3CAA23-00B9-11d2-9DFB-00C04FA322BA}
Corresponding Event = onarrival
** Have you registered your sink COM class on this machine?

The error I got is “Permission denied” – of course, I have to run it with administrative privileges. But wait, I _am_ running it with such privileges!
Had no clue on what is happening. Checked if the mentioned class (CDO.SS_SMTPOnArrivalSink) is registered or not – it was. Checked NTFS permissions on cdosys.dll – seemed OK (I even granted full access to Everyone with no luck). That was time for… wait for it… Process Monitor! (great tool, indeed)

And there it was: cscript.exe (the process running smtpreg.vbs) is failed to get write access to the registry for the entry HKCR\CLSID\{CD000005-8B95-11D1-82DB-00C04FB1625D}, which is the CLSID of “SMTP OnArrival Script Host Sink Class”. Since smtpreg.vbs is something I do not want to mess with, I decided to go with the easier solution: give write permissions to admins for the forementioned registry key.

We all know the drill: regedit, search for the CLSID, right click, Permissions, check “Full Control” for the Administrators group, Apply… and got “Cannot set permissions … – access is denied”. This is because only the TrustedInstaller user has “Full Control” permissions over these registry keys, others only has “Read” access.

The solution: take ownership of this registry entry (right click on the entry / Permissions / Advanced / Owner tab / Change ownership to administrators). After applying the changes I was able to give Full Control to Administrators and run smtpreg.vbs successfully.

cscript smtpreg.vbs /add 1 onarrival NoreplyHandler CDO.SS_SMTPOnArrivalSink “rcpt to=noreply@*”
Microsoft (R) Windows Script Host Version 5.8
Copyright (C) Microsoft Corporation. All rights reserved.

Binding Display Name Specified: NoreplyHandler
Assigning priority (24575 in 32767)
** SUCCESS **
Registered Binding:
Event Name :SMTP Transport OnSubmission
Display Name:NoreplyHandler
Binding GUID:{8CA00335-FF90-47E6-A1F2-BAA29926EFDC}
ProgID :CDO.SS_SMTPOnArrivalSink
Rule :rcpt to=noreply@*
Priority :24575 (0 – 32767, default: 24575)
ComCatID :{FF3CAA23-00B9-11d2-9DFB-00C04FA322BA}

cscript smtpreg.vbs /setprop 1 onarrival NoreplyHandler Sink ScriptName “c:\smtp_ext\noreply\noreply.js”
Microsoft (R) Windows Script Host Version 5.8
Copyright (C) Microsoft Corporation. All rights reserved.

Binding Display Name Specified: NoreplyHandler
set property ScriptName to c:\smtp_ext\noreply\noreply.js

The sink quoted above is a simple SMTP event sink that consumes emails sent to a given address, as we do not want to deal with emails arriving to noreply@ addresses. There are many other things that event sinks are usable for. If you are interested in this powerful technique we have a few sample event sinks on our web site to start with:
Simple Attachment Filtering
Remove Read Receipt Requests on The Server