Hi jsrit,
I’m sorry to hear you ran into this issue, and what you’re describing unfortunately sounds like a result of how Yahoo has designed their emails to work more recently. Essentially, using a Yahoo email as both the From Email and the Send To Email Address is likely to trigger these security measures that Yahoo added (which to my understanding, are meant to help prevent Yahoo emails from being used for spamming). However, this is just one piece of the puzzle in terms of email delivery as a whole.
Further, these kinds of delivery issues take place after our plugin has sent the email out — so there isn’t a way for our plugin to detect whether the email delivered successfully.
This is why we highly recommend using an SMTP plugin like you mentioned, and we’ve been working to further promote testing all forms prior to launching them on a page/post.
As part of this, we’re also working to add extra details within our plugin to encourage more users to both test for email issues and to consider using SMTP. Fortunately email delivery issues only impact a small percentage of users, but of course we don’t want anyone discovering issues like this post-launch.
Thank you for the feedback, and if you have any questions please feel welcome to post those in our Lite support forum. Thanks!
