Simple tip this afternoon. You may have got the following error when sending emails through ASP.Net’s built in mail server before:

From: postmaster@YourWebserversName [mailto:postmaster@YourWebserversName] 
Sent: 25 June 2010 13:22
To: sender@sendingdomainname.com
Subject: Delivery Status Notification (Failure)

This is an automatically generated Delivery Status Notification.

Delivery to the following recipients failed.

      recipient@recievingdomainname.com

Reporting-MTA: dns;YourWebserversName
Received-From-MTA: dns;YourWebserversName
Arrival-Date: Fri, 25 Jun 2010 13:21:30 +0100

Final-Recipient: rfc822;recipient@recievingdomainname.com
Action: failed
Status: 5.5.0
Diagnostic-Code: smtp;504 <YourWebserversName>: Helo command rejected: need fully-qualified hostname

The fix is easy:

1. Open IIS
2. View the properties of you Default SMTP Virtual Server
3. Go to the “Delivery” tab
4. Click the “Advanced” button (in the bottom right corner)
5. Under “Fully-qualified domain name” enter a domain name that points to the server
6. Click Ok until you’re back to IIS

If you're not configuring Umbraco through a web installer, you've had your installs in place for years and never checked the permissions or whoever set the permissions up was lazy and gave IIS write access to the entire folder, there will come a time when you want to restrict modify access to just those user(s) who should have access.

You can find a (pretty) complete list of the files/folders that the Umbraco install should have access to here but assigning them across 101 different installs is a PITA . Thanks to a helpful PowerShell script to set folder permissions from PowerShell.nu you can easily automate the process.

For those of you not familiar with PowerShell (like me) complete instructions are below. For the rest, here's the command:

Get-ChildItem -path ##PATH TO YOUR INSTALL## 
| Where { $_.name -eq "Bin" -or $_.name -eq "Config" -or $_.name -eq "Css" -or $_.name -eq "Data" -or $_.name -eq "Masterpages" -or $_.name -eq "Media" -or $_.name -eq "Scripts" -or $_.name -eq "Umbraco" -or $_.name -eq "Umbraco_client" -or $_.name -eq "UserControls" -or $_.name -eq "Xslt" } 
| ForEach {./SetFolderPermission.ps1 -path $_.Fullname -Access "NETWORK SERVICE" -Permission Modify}

Instructions:

1. Save the SetFolderPermission.ps1 script to your server
2. Open your PowerShell console (I think it's installed by default if not, you can download PowerShell here)
3. Copy the above PowerShell command into notepad
4. Update "##PATH TO YOUR INSTALL##" to your Umbraco install
5. If your IIS install doesn't use NETWORK SERVICE as the default user, update it to your user
6. Make sure it's all on a single line
7. Copy/Paste/Run in PowerShell

Bonus

If you're uber lazy and just have a web folder of Umbraco installs you can set the path to the folder of Umbraco installs and use:

Get-ChildItem -path ##PATH TO YOUR FOLDER## -recurse
| Where { $_.name -eq "Bin" -or $_.name -eq "Config" -or $_.name -eq "Css" -or $_.name -eq "Data" -or $_.name -eq "Masterpages" -or $_.name -eq "Media" -or $_.name -eq "Scripts" -or $_.name -eq "Umbraco" -or $_.name -eq "Umbraco_client" -or $_.name -eq "UserControls" -or $_.name -eq "Xslt" } 
| ForEach {./SetFolderPermission.ps1 -path $_.Fullname -Access "NETWORK SERVICE" -Permission Modify}

I've not tried this mind you and can't recommend it but hey, it's there if you want it ;)