I have registered members to my website. I have a really important announcement. I already have C# coded email sending software but emails drops spam folder. What precautions i can take to prevent dropping spam folder. I asked several mass email company about my issue that i want to buy like 350k email service but none of them replied my emails. The environment is Windows Server 2008 IIS Server 7.5 Netframework 4.0 I am planning to add only text no link or images. I suppose adding images or links would increase my emails to drop spam box. You can tell me modifications on my software or on my iis server or i am also open to affordable mass email companies.