Emails going to Spam

Hi,
I am using this plugin which came as a bundle with nex theme, my issue is that all the Emails i get from the website is received with a “[SPAM]” text in the subject line and forwarded to the spam folder i have already followed your tutorials
1. https://ninjaforms.com/docs/troubleshooting-email-problems/
2. https://ninjaforms.com/why-your-email-gets-sent-to-spam-quick-tips-to-keep-out-of-the-can/
But Still doesn’t seem to work.

The Emails are working flawlessly with CF7 plugin but this theme is requiring me to use your plugin to work properly, so please help me out here.

Thanks.