As you've probably noticed by now I'm working with Nintex at the moment.

Yesterday I was trying to create a workflow that had to send a notification to a user. I added my smtp server and a from address to the Nintex outgoing email settings. Be aware that you have to set the Nintex outgoing email settings separately from the outgoing email settings for the rest of your farm. This is because  Nintex uses System.Net.Mail.SmtpClient.Send where as SharePoint itself uses SPUtility.SendEmail  (thanks Gerard!). So Nintex doesn't take over the farm settings for outgoing email and theoratically you could use a different smtp server or from address for Nintex workflow. Now that I write it down I realise that this last fact might be the reason why they use different settings. To give you the opportunity to define a specific from address for emails send from workflows.

Anyway, even after I added my smtp server and from address to both my SharePoint farm and Nintex settings page I still received errors that emails could not be send as no from address was specified. I didn't understand why that would happen so I opened up Bing (I really like Bing, and I love the background pictures) to try and find other people with the same problem and preferably a solution too. I didn't find anyone with the same problem, nor did I find a clear solution, but I did find someone that was having problems with other Nintex related settings that he traced down to being caused by using IIS 7.0 (and Windows Server 2008) as opposed to using IIS 6.0. As it happens I'm using Windows Server 2008 with IIS 7.0 as well. So I decided to have a closer look at IIS 7.0 and also fill in my smtp server in the IIS 7.0 settings.

This did the trick. My emails are being send without a problem now. I didn't investigate any further as to what is causing this somewhat weird behaviour. It might have something to do with the firewall. I might do a bit more investigating later on, but as others may have the same problem I decided to at least post the solution I found now…

Hope this can help others.