HOW TO get notification when SMTP mails are received

Question

hi Need to setup a SMTP server within my C# server application to be able to receive incoming email message from other email exchange server. We are not using any post office (no POP3 no IMAP etc) Right now we have figured out that we can config the server to automatically store the received mail to some local folder. Then we need to read the mail from that location. The problem now is: How can we be notified when there is new mail?? Is polling the only way? I've read some low-level stuff about IIS events/sinks (deep stuff) eg. IIS OnSubmission event versus CDONT's CDO_OnArrival event. Cannot seem to make sense of that stuff. Can that be used to do the notification? Any code samples? Any help or thots wd be greatly appreciated soonest!!! ThanksSS!

chrishornberger · Answer

No idea on the file format... yet. So you're using the built-in SMTP server in Windows Server/IIS? I'll take a look and see what I can find out. Goody something to do today :) Regarding the FWF No it's based on polling. Could have gone either way But I wanted the control polling gives me. It was written for a specific paradigm where (semi)known filenames are being received into a folder rather than a hodgepodge of potential filenames like the (probable) case with the SMTP server. It's very extensible. In fact my production version running at my day job has two handlers that don't do anything at all with files they're just containers for timers to do scheduled jobs. I'm working on a more solid and flexible design that's simply called the Jobber Framework that abstracts a little more away from the FileWatcher model. It will still have a filewatcher codebase but it will lend itself more freely to other things (like the schedule handler I mentioned) and will have more intrinsic support for utility type functionality that the handlers can call back to mama for. Things like setting/data persistence (some of that is there now) email/logging (again some is there) etc. Hopefully when it's done a handler class will be as simple as extending one of the basehandlers (file timer tcp port etc) and writing a custom (DoProcessing(...)) override and *poof* instant job engine plug it. It's *almost* that easy now. :) Thank you for your interest.

annie.kok · Answer

Thanks for your ideas & your offer to help! You sound like an expert parser does that occupy your night jobs too? ;-) Believe mail messages have their own file in the Drop folder. Not sure about attachments. However this is based on what I read at: http://msdn.microsoft.com/library/en-us/dnproasp2/html/howsmtpserviceworks.asp?frame=true However haven't verified this. Anyone can confirm this? Have no idea what the file format is. If I knew then parsing wouldn't be a problem I guess. So what's the format of the file in the Drop folder? Can't check myself as our IIS server is not ready. Would be grateful if anyone has sample files. Btw is the Filewatcher Framework on www.chornbe.com anything to do with the FileSystemWatcher class mentioned by jamesdivine?

chrishornberger · Answer

And if my assumptions are correct as indicated in earlier emails the FileSystemWatcher will help you out here.

chrishornberger · Answer

Ah... I guess I misunderstood your earlier posts. I thought you were trying to customize some SMTP-like functionality. Well then... As I understand it each message comes in and is deposited in to the Drop folder in its own file (or files in the case of attachments?) right? Or is the file some shaped data container that houses many messages? If it's per-file based then you're looking at simply opening the file(s) parsing and possibly doing some Base64 stuff. Nothing big-n-bad. Regular expressions and/or some rules based parsing is what you'll want to use. I'd be glad to help out with this if you like. I actually like text parsing and thanks to my day job I've gotten pretty good at it. We exchange files with client banks and mainframes all day long. wheeeeeeeeee.

annie.kok · Answer

hi chornberger Rihan jamesdivine and all w3c RFCs.. sounds like Greek to me but thanks for the tips & the link! Perhaps I've not explained it that clearly. We're not trying to duplicate the SMTP service. But just to pick up those emails that come in for the local address via SMTP. Preferably to be notified when these mails come in rather than polling for them. After the SMTP service is done these locally addressed mails would be found in the Drop folder. (standard behaviour) As I understand most folks use POP3 so the mails go into different mailboxes and I've seen C# libraries that use POP3 to retrieve the mails. Ours is a server program that retrieves the mails and we don't need the POP3 mailboxes. One solution is to grab those mails after they are deposited in the Drop folder. So does anyone know where I can find any C# libraries for that? Eg. Exchange? CDO? anything? The 2nd solution is to use event sinks for Store Data just before SMTP service puts the locally addressed mails in the Drop folder. It's been so hard finding people who have tried out retrieving mails WITHOUT POP3 or IMAP. *sigh* Thanks to all for responding! (was getting disheartened when all was quiet after I posted)

chrishornberger · Answer

hmm... bizarre. I'd get new management :) But seriously it sounds far more like a financially motivated decision than a sound business one. Little choice but to delve into the w3c RFCs and get to know the protocol and see what can and can't be done. There's some SMTP-receive information in this thread: http://www.ornl.gov/cts/archives/mailing-lists/qmail/2002/08/threads.html#00221 I don't know how helpful it will be. Check the RFCs before you go any further.

james · Answer

I asked the same question take a look at this thread http://216.26.160.137/Forums/AspNetForums20/ShowPost.aspx?PostID=1394#1414

chrishornberger · Answer

And by the way how does one retrieve SMTP mails from the Drop folder using C# when it's just plain SMTP? Cannot find any .NET support for such email retrieval.  Generally SMTP is used for outbound mail relaying and *normally* gets configured to handle this itself. Stepping back from your particular and specific technical questions a moment I feel compelled to ask why you're reinventing this particular wheel? Is this an academic excercise or are you doing something very unusual in regards to SMTP mail relaying?

Rihan.Meij · Answer

Hi There is quite a bit of examples on how to write that event sink if you search for Exchange 2000 event sink and disclaimerers. Have not written one myself so good luck hope you find some stuff Cheers Rihan

annie.kok · Answer

Yes in a way the messages are in some kind of file. Cos we are using plain SMTP (no POP3 no IMAP) the messages will be automatically stored in the default SMTP incoming folder ie. Drop folder. Thanks for your suggestion on FileSystemWatcher I'll go check it out. Anyone has any other ideas? And by the way how does one retrieve SMTP mails from the Drop folder using C# when it's just plain SMTP? Cannot find any .NET support for such email retrieval. I've already gone through the examples at the Internet & Web corner. All the examples I've seen assume there's a POP3 or IMAP server. Urgent.. Please help... Thanks a lot...

james · Answer

If you are storing the messages in a text file or some other type of data file you may be able to use the FileSystemWatcher class to raise an event when a new file is created. While this is still polling its automated polling and would provide a higher level solution that using CDO. look at this article for more http://www.c-sharpcorner.com/3/FSWatcherMB.asp -James