Review on Verify Email by Jake Pavelko

It's easy enough for anyone with basic computer skills, yet robust in its capabilities (both technical & user interface).

The free version is limited but it does what I need at this time so no complaints there! We've been using verifyemail as part of our anti-spam solution since about 2013/2014 when we first started working wtih them then they were called "Mailguard". They have continued their good work over many years now - great customer service team who are always helpful without being pushy which makes all customers feel valued even if you're paying out money each month ;).