I have a web application that requires a server based component to periodically access POP3 email boxes and retrieve emails. The service then needs to process the emails which will involve:
Validating the email against some business rules (does it contain a valid reference in the subject line, which user sent the mail, etc.)
Analysing and saving any attachments to disk
Take the email body and attachment details and create a new item in the database
Or update an existing item where the reference matches the incoming email subject line
What is the best way to approach this? I really don't want to have to write a POP3 client from scratch, but I need to be able to customize the processing of emails. Ideally I would be able to plug in some component that does the access and retrieval for me, returning arrays of attachments, body text, subject line, etc. ready for my processing...
[ UPDATE: Reviews ]
OK, so I have spent a fair amount of time looking into (mainly free) .NET POP3 libraries so I thought I'd provide a short review of some of those mentioned below and a few others:
Pop3.net - free - works OK, very basic in terms of functionality provided. This is pretty much just the POP3 commands and some base64 encoding, but it's very straight forward - probably a good introduction
Pop3 Wizard - commercial / some open source code - couldn't get this to build, missing DLLs, I wouldn't bother with this
C#Mail - free - works well, comes with Mime parser and SMTP client, however the comments are in Japanese (not a big deal) and it didn't work with SSL 'out of the box' - I had to change the SslStream constructor after which it worked no problem
OpenPOP - free - hasn't been updated for about 5 years so it's current state is .NET 1.0, doesn't support SSL but that was no problem to resolve - I just replaced the existing stream with an SslStream and it worked. Comes with Mime parser.
Of the free libraries, I'd go for C#Mail or OpenPOP.
I looked at a few commercial libraries: Chillkat, Rebex, RemObjects, JMail.net. Based on features, price and impression of the company I would probably go for Rebex and may in the future if my requirements change or I run into production issues with either of C#Mail or OpenPOP.
In case anyone's needs it, this is the replacement SslStream constructor that I used to enable SSL with C#Mail and OpenPOP:
SslStream stream = new SslStream(clientSocket.GetStream(), false,
delegate(object sender, X509Certificate cert,
X509Chain chain, SslPolicyErrors errors) { return true; });
