There are a number of factors that can contribute to your messages going to the junk folder. Reputation is a large one, especially when you have had spam complaints. Template design and construction, content and subject line all play their part.
If you really want to send everything in-house, please make sure you are not using your transactional domain for your marketing, and that your lists are of good quality. You must also make sure your template is of good build - its not just the same as a webpage!
Using a specialist for email marketing can save a lot of time and money - you can still do everything yourself but you use an ESP (Email Service Provider) who manages their servers and email reputation of all their customers - and help with templates to make sure you get in the inbox and improve your open rate/click throughs.
There are many ESPs out there - many very good and well priced. We at FrogEmail
have over 100 html email templates already in our system for you to customise or we can create a bespoke one for you (unless you have the knowledge in which case you can upload your own template).
If you would like to discuss our email marketing
services further, or would just like some general advice - feel free to contact me.