ASP.NET "5.7.1 Unable to relay for email" when SmtpClient.UseDefaultCredentials = true


Was looking at a problem with Andy regarding using SmtpClient.UserDefaultCredentials = true, and sending emails within an authenticated WCF service.

We can send emails within the domain without any issues, but when sending emails outside of the domain the mail server rejects us with the 5.7.1 Unable to relay for [email protected]

The easier fix would probably be to UseDefaultCredentials = false, and specify a NetworkCredential(username,password).  But we were stubborn and didn’t want to have to enter a email address somewhere in the web.config.

While investigating – we realized that if we specify the mail server by IP address instead of DNS name – then the email will be delivered.


Our suspicions are that the Exchange mail server has different rule sets to decide if it trusts the source to be somewhere local.  If the IP address specified is a local network IP – it seems to relax the relay rules somewhat.

SharePoint 2010 Speed, and Boot to VHD

Been pouring through all the new goodies in SharePoint 2010 like a kid opening his first Christmas present -
So much fun, so little time.

A few people have made the comment that SharePoint 2010 Public Beta runs pretty slowly for demo’s – here’re a few suggestions I’ve noticed that helps for me:

  1. You need more than 2GB of RAM for SharePoint on your demo machine. 
  2. Ideally, a generous amount of hard drive space

My setup has worked pretty well for me:

  1. Host is Win7 x64
  2. Created a VHD (virtual hard drive) with about 50GB allocated space. 
  3. Installed Windows 2008 R2, SQL Server 2008, SharePoint 2010 public beta, Office Web Apps, and Office 2010 client apps.
  4. Configure the VHD as a bootable device (new in Win7)
  5. On start of laptop, I get to choose to boot into Windows 2008 / SharePoint 2010 directly, which allocates all the laptop’s resources to the VM
  6. Oh – grab the ATI display drivers for DELL (see my previous post) to make sure Windows 2008 R2 can display via an external projector – ahead of the presentation.  (I nearly had a panic attack but got it all sorted before I had to go on stage).

The best part is when we move on from the public beta, I’ll just copy a new VHD over the same directory under Win7, then it’s all set.

ATI x64 driver fail - Catalyst Install Manager has stopped working

This could possibly be the last ATI product that I'd purchase.  For almost as long as I could remember I can not get the ATI drivers to install.

  • Download from ATI website
  • Download beta from ATI website
  • Download from Dell website

I've always had to rely on Windows Update - but then it doesn't come with the Catalyst utilities.


Today I was forced to upgrade the drivers...

  • Running Boot to VHD on the machine with Windows Server 2008 R2 x64 installed
  • Default driver that Windows Update picked up is the Generic one
  • I need to be able to use an external monitor for presentation tomorrow - Yikes!

Fortunately, I found my solution here:

To cut a long story short - this worked for me:

bin64\ATISetup.EXE –install –output SCREEN


The iPhone design flaw

Hi Apple,

When I first got my iPhone it truly was a thing of joy. New apps were being created and continued to blew away my expectations of what a phone can do.

Not anymore, I have not found anything worth downloading or buying in the last month. I've browsing through the paid apps section now and filtering anything above $10. Still nothing that I'd consider truly must-have.

I will not buy anything above $10 for a platform that I’m considering to abandon in the next cycle.

I gave up a bit.
I cleaned out my iPhone apps list, call it a defrag, if you will - it is now down to only 20. At its height I had well over 7-8 pages full of apps.


I don't know what it is that you are doing - but perhaps it's also what you are NOT doing.

Whatever it is, I call it a design flaw.


Please bring back the developers and the great apps.  Otherwise you will lose your users - me.  There are plenty of other mobile vendors that are eyeing your market and they will happily take your developers from you.

I remember the days when I was using a Mac and we had no software.  I don’t know if you had forgotten those dark days.

SharePoint 2010 – sneak peek

Microsoft has begin to move and has blasted off with the SharePoint 2010 sneak peek website – I can’t help but think the timing was strategic – right after the NZ SharePoint conference, before the US SharePoint conference coming up in October.  If this had go up one week before the NZ SharePoint conference – there would have been many speakers ambushed with questions they might not know how to answer.

Anyway, the areas I’ll be paying extreme close attention to are:


  • Love the ribbon!
  • Love the cross browser support!
  • Love the AJAX – though the video looks like there were still full screen refreshes
  • Curious about Visio services
  • Curious about Business Connectivity Services
  • Like the SharePoint designer – wish they allow more admin control to turn off features so that it can be more accepted in the enterprise.


  • Like new central admin
  • Love SharePoint best practice analyzer!
  • Love usage reporting and logging!
  • Love the unattached content database recovery!


  • Curious about VS.NET 2010 integration – I hope it’s heaps better than VSeWSS 1.3
  • Love LINQ for SharePoint!
  • Curious about Developer Dashboard
  • Love client object model!

Anyway, lots of love for now – no hate yet.