I got also the same problem. Tried using PHP mailer: Blesta said "Sent" but the email never arrives. Tried using SMTP (own server/cPanel and Sendgrid): Blesta said "The email failed to send due to a configuration issue", email also never arrives. The simplest solution that works for me: I had to change my email address (sender) from email@example.com to firstname.lastname@example.org sending emails from root domain never works despite which SMTP server I use (also tried all configs: SSL, TLS, and Non-SSL). Don't know what the cause.