Sending emails is easy, by using the SPUtility.SendEmail function. Well, at least it should be easy. There are a lot of code samples, so search around for some if you need it. However, again I ran into a SharePoint problem. This function returns a boolean value and gave me 'false' all the time. I tried to use the ordinary mail method of System.Net.Mail. There I got an error about "Message rejected as spam by Content Filtering". Some research of the IT department on Exchange did not solve this problem.
Well, I went back to the SPUtility.SendEmail function. I turned out that using the StringDictionary gave some problems as well as using HTML tags. Using plane text and one of the other overloads that doesn't use the StringDictionary results in a successful send action. But I needed a formatted message (sending some links).
The LOG files gave some extra information on the 'false' action. And yes, it shows why it didn't send the messages: 550 5.7.1 Message rejected as spam by Content Filtering.
The solution I found (here) was relatively easy. Bypassing the content filter for a specific email address (or even sender domain). To do this, you need to resort to the Exchange shell (EMS) to manage it.
- Click on Start > All Programs > Microsoft Exchange 20xx > Exchange Management Shell. Note, this works for at least Exchange 2007 and 2010 versions.
- Create the bypass for the 'from' email address you use when sending the email from a timer job:
Set-ContentFilterConfig -BypassedSenders firstname.lastname@example.org, email@example.com
Note: You need to realize that spammers can spoof the 'from' address and this would allow spam to get thru.
So, after all, it was not really a SharePoint problem, but an Exchange 'problem'.