We recently had a client who had this problem. Emails weren’t being sent to him from WordPress and as such he was missing most of his leads and potentially large amounts of revenue was going wanting. We solved the problem and made a video about it. Our expertise in WordPress Support meant we’d seen this before. Watch it below.
As you can see this time it’s a case of your email server believing the server that your web is hosted on is responsible for spammy activity due to the actions that other people using that host server. Try this fix and see if that resolves the problem.
You might think that changing your hosting provider would solve the issue but you’re better off simply solving the issue. You never know when it might happen again. You could simply end up getting your site hosted on another server that has the same problem or develops the same problem.
And remember you can see the results of people filling in your forms by hovering over the forms button and clicking on entries, at least with Gravity Forms you can. You should probably be using Gravity Forms if you aren’t.