Mailtester.com was a lifesaver throughout these years.
I do indeed have a hard time before knowing this product. There are many email address I can’t verify through Rapportive and ended up excluding leads or delivering some as noted as an unverified email address.
But thanks all to Mailtester.com, I have been sure that the email address list I have provided is valid.
I do often use this. If I can’t get any from Rapportive, I’ll go to email-format.com, and then Mailtester.com.