Friday, January 15, 2010

Writing a simple scripted process to download attachmentts in Exchange 2007/ 2010 using the EWS Managed API

Every complicated thing in life is made up of smaller simpler building blocks, when it comes to writing a script (or any code really) the more of these little building blocks you have to figure out the more the process of solving a problem can become bewildering. The Internet generally provides you with lots of half eaten sandwiches of information something someone else has taken a bite out but a lot of the time half done, and as with any code its usefulness declines over time as new and better API's and methods are derived. In this post I'm going to go through a simple scripted process that hopefully covers a few more of these smaller building blocks that you might face when asked to come up with a simple costless solution to perform an automated business function with a script.

So the process im going to look at is one that comes up a lot and that is you have an Email that comes into to certain mailbox every day with a certain subject in my case "Daily Export" this email has an attachment that must be downloaded to a fileserver. After the message is downloaded the email should then be moved into a processed folder which is a subfolder of the inbox of the mailbox and marked as Read.

So first this script will be designed to be run once a day from a scheduled task. First off with this script is we need a few variables that need to be hardcoded with some settings.

$MailboxName = "user@mailbox.com"

This is the emailaddress of the mailbox the script is going to retrieve the message from

$Subject = "Daily Export"

This is the subject of the Email that has the attachment to process.

$ProcessedFolderPath = "/Inbox/Processed"

This is the Folder path to where the message is going to moved to this is needed for the fuction that will find the FolderID of this folder which is important when you go to move messages with EWS.

$downloadDirectory = "c:\temp\"

This is the folder where attachments will be downloaded to

The next part of this script is the FindTargetFolder function this is a function that takes a folderpath in the format of /FirstLevelFolder/SecondLevelFolder etc and then uses this to find the folderID of the folder when the email once processed will be moved to.

The next part of the script is some standard EWS Managed API Powershell stuff that I've talked about a lot before in this post

Then we come to the search filter which is a little interesting this search filter is doing a bitwise AND which means that all three conditions must be meet for it to return items.

$Sfir = new-object Microsoft.Exchange.WebServices.Data.SearchFilter+IsEqualTo([Microsoft.Exchange.WebServices.Data.EmailMessageSchema]::IsRead, $false)
$Sfsub = new-object Microsoft.Exchange.WebServices.Data.SearchFilter+IsEqualTo([Microsoft.Exchange.WebServices.Data.ItemSchema]::Subject, $Subject)
$Sfha = new-object Microsoft.Exchange.WebServices.Data.SearchFilter+IsEqualTo([Microsoft.Exchange.WebServices.Data.EmailMessageSchema]::HasAttachments, $true)
$sfCollection = new-object Microsoft.Exchange.WebServices.Data.SearchFilter+SearchFilterCollection([Microsoft.Exchange.WebServices.Data.LogicalOperator]::And)
;

So what this filter does is looks for Emails that are unread, have attachments and have a subject "Daily Export". If all these are true then these items will be returned into the finditems collection which brings us to the next part of the script.

$miMailItems.Load()
foreach($attach in $miMailItems.Attachments){
$attach.Load()
$fiFile = new-object System.IO.FileStream(($downloadDirectory + “\” + $attach.Name.ToString()), [System.IO.FileMode]::Create)
$fiFile.Write($attach.Content, 0, $attach.Content.Length)
$fiFile.Close()
write-host "Downloaded Attachment : " + (($downloadDirectory + “\” + $attach.Name.ToString()))
}
$miMailItems.isread = $true

This part of the script loads the messsages and then loops through the attachments and downloads them to the specified path.

$miMailItems.isread = $true
$miMailItems.Update([Microsoft.Exchange.WebServices.Data.ConflictResolutionMode]::AlwaysOverwrite)

These two lines set the message to read and then updates it.

[VOID]$miMailItems.Move($Global:findFolder.Id.UniqueId)

This last line moves the message to the processed folder.

That's it although generally not really but its as far as this half eaten sandwich is going to go but its pretty easy from here. I've put a download of this script here