Skip to main content

Email and Attachment Archiving with a Transport Agent on Exchange 2007

I’ve been continuing on with building and learning about Transport Agents over the past couple of weeks and thought I’d share an agent I’ve found useful. The following agent is a simple archiving agent it saves the serialized version of the message from the Mimedocument class to an eml file in a directory assigning it a GUID as a filename to make sure its unique. It also enumerates though the attachments of a message and saves them to a separate directory using the attachment filename and the message guid to link the message and attachments. I also added some code into to delete pdf files that where smaller than 20 KB this was for testing purposes but it’s something I’ve used in the past in SMTP sinks to overcome certain issues.

Like the last Agent I posted this is a Routing agent I’m running on Hub Server the code is relatively simple to follow. To do the attachment processing I’ve used the new EmailMessage class that’s part of the Microsoft.Exchange.Data.Transport.Email namespace. The cool thing about this class is it does provide a level of abstraction above TNEF and MIME. So if say you’re sending a meeting appointment internally to another user and you have attached a document if you where to parse this at the MIME level the message and attachment would be in TNEF format (good old winmail.dat) but the EmailMessage class allows you to enumerate though any attachments in the calendar invitation without needing to worry about using the lower level TNEF parsers. The one complaint I have about this class is that downloading an attachment is a little bit of a pain. After initially having problems with streams that would get corrupted intermittently I found Jon Skeet’s page http://www.yoda.arachsys.com/csharp/readbinary.html which had a function that worked well.

The other challenge I had was with removing particular attachments, generally deleting objects while enumerating though a collection isn’t the best of programming practices. Sometimes enumerating the collection in reverse can overcome this issue but for some reason when I did this with the attachment collection it would always give me an issue when I removed an attachment. So the solution I came up with for this was just to store the attachments that I wanted to delete in an arraylist during the initial attachment check and then loop though the arraylist at the end and delete those objects which seemed to work okay.

The one thing this agent is yet to handle is processing attachments within embedded messages which I think will be a separate post.

I’ve put a download of the code from this post here the code itself looks like

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Diagnostics;
using Microsoft.Exchange.Data.Transport;
using Microsoft.Exchange.Data.Mime;
using Microsoft.Exchange.Data.Transport.Email;
using Microsoft.Exchange.Data.Transport.Smtp;
using Microsoft.Exchange.Data.Transport.Routing;
using Microsoft.Exchange.Data.Common;

namespace msgdevExchangeRoutingAgents
{
public class EmailArchivingFactory : RoutingAgentFactory
{
public override RoutingAgent CreateAgent(SmtpServer server)
{
RoutingAgent raXheader = new EmailArchivingRoutingAgent();
return raXheader;
}
}
}

public class EmailArchivingRoutingAgent : RoutingAgent
{
public EmailArchivingRoutingAgent()
{
base.OnSubmittedMessage += new SubmittedMessageEventHandler(EmailArchivingRoutingAgent_OnSubmittedMessage);
}

void EmailArchivingRoutingAgent_OnSubmittedMessage(SubmittedMessageEventSource source, QueuedMessageEventArgs e)
{
//Archive Message
String MessageGuid = Guid.NewGuid().ToString();
Stream fsFileStream = new FileStream(@"C:\temp\archive\messages\" + MessageGuid + ".eml", FileMode.OpenOrCreate);
e.MailItem.Message.MimeDocument.WriteTo(fsFileStream);
fsFileStream.Close();
//Archive Any Attachments Check for pdf attachments under 20 K and delete
ArrayList adAttachmenttoDelete = new ArrayList();
for (int index = e.MailItem.Message.Attachments.Count - 1; index >= 0; index--)
{
Attachment atAttach = e.MailItem.Message.Attachments[index];
if (atAttach.AttachmentType == AttachmentType.Regular & atAttach.FileName != null)
{
FileStream atFileStream = File.Create(Path.Combine(@"C:\temp\archive\attachments\", MessageGuid + "-" + atAttach.FileName));
Stream attachstream = atAttach.GetContentReadStream();
byte[] bytes = ReadFully(attachstream, (int)attachstream.Length);
atFileStream.Write(bytes, 0, bytes.Length);
atFileStream.Close();
atFileStream = null;
bytes = null;
// Find Any PDF attachments less then 20 KB
if (atAttach.FileName.Length >= 3)
{
String feFileExtension = atAttach.FileName.Substring((atAttach.FileName.Length - 4), 4);
if (feFileExtension.ToLower() == ".pdf" & attachstream.Length < attachstream =" null;" atattach =" null;" enumerator =" adAttachmenttoDelete.GetEnumerator();" initiallength =" 32768;" buffer =" new" read =" 0;" chunk =" stream.Read(buffer,"> 0)
{
read += chunk;

// If we've reached the end of our buffer, check to see if there's
// any more information
if (read == buffer.Length)
{
int nextByte = stream.ReadByte();

// End of stream? If so, we're done
if (nextByte == -1)
{
return buffer;
}

// Nope. Resize the buffer, put in the byte we've just
// read, and continue
byte[] newBuffer = new byte[buffer.Length * 2];
Array.Copy(buffer, newBuffer, buffer.Length);
newBuffer[read] = (byte)nextByte;
buffer = newBuffer;
read++;
}
}
// Buffer is now too big. Shrink it.
byte[] ret = new byte[read];
Array.Copy(buffer, ret, read);
return ret;
}
}




Popular posts from this blog

Downloading a shared file from Onedrive for business using Powershell

I thought I'd quickly share this script I came up with to download a file that was shared using One Drive for Business (which is SharePoint under the covers) with Powershell. The following script takes a OneDrive for business URL which would look like https://mydom-my.sharepoint.com/personal/gscales_domain_com/Documents/Email%20attachments/filename.txt This script is pretty simple it uses the SharePoint CSOM (Client side object Model) which it loads in the first line. It uses the URI object to separate the host and relative URL which the CSOM requires and also the SharePointOnlineCredentials object to handle the Office365 SharePoint online authentication. The following script is a function that take the OneDrive URL, Credentials for Office365 and path you want to download the file to and downloads the file. eg to run the script you would use something like ./spdownload.ps1 ' https://mydom-my.sharepoint.com/personal/gscales_domain_com/Documents/Email%20attachments/filena

Export calendar Items to a CSV file using EWS and Powershell

Somebody asked about this last week and while I have a lot of EWS scripts that do access the Calendar I didn't have a simple example that just exported a list of the Calendar events with relevant information to a CSV file so here it is. I've talked on this one before in this howto  but when you query the calendar folder using EWS you need to use a CalendarView which will expand any recurring appointments in a calendar. There are some limits when you use a calendarview in that you can only return a maximum of 2 years of appointments at a time and paging will limit the max number of items to 1000 per call. So if you have a calendar with a very large number of appointments you need to break your query into small date time blocks. In this example script I'm just grabbing the next 7 days of appointments if you want to query a longer period you need to adjust the following lines (keeping in mind what I just mentioned) #Define Date to Query $StartDate = (Get-Date) $EndDate

How to test SMTP using Opportunistic TLS with Powershell and grab the public certificate a SMTP server is using

Most email services these day employ Opportunistic TLS when trying to send Messages which means that wherever possible the Messages will be encrypted rather then the plain text legacy of SMTP.  This method was defined in RFC 3207 "SMTP Service Extension for Secure SMTP over Transport Layer Security" and  there's a quite a good explanation of Opportunistic TLS on Wikipedia  https://en.wikipedia.org/wiki/Opportunistic_TLS .  This is used for both Server to Server (eg MTA to MTA) and Client to server (Eg a Message client like Outlook which acts as a MSA) the later being generally Authenticated. Basically it allows you to have a normal plain text SMTP conversation that is then upgraded to TLS using the STARTTLS verb. Not all servers will support this verb so if its not supported then a message is just sent as Plain text. TLS relies on PKI certificates and the administrative issue s that come around certificate management like expired certificates which is why I wrote th
All sample scripts and source code is provided by for illustrative purposes only. All examples are untested in different environments and therefore, I cannot guarantee or imply reliability, serviceability, or function of these programs.

All code contained herein is provided to you "AS IS" without any warranties of any kind. The implied warranties of non-infringement, merchantability and fitness for a particular purpose are expressly disclaimed.