apa-sl

Problem solved.

Got it. What a stupid mistake… In the ‘reply-to’ additional header I’ve made a typo and instead of [contact_mail] I’ve used [contact-mail].

After correcting this typo combo Postman+CF7 is sending emails both trough plain smtp authentication and trough gmail.

Small update: I have the same problem on another WP where I’ve configured Postman to use Gmail SMTP with oAuth login. Test email is being delivered, but the contact form 7 started to display ‘Failed to send your message. Please try later or contact the administrator by another method.’ when trying to send a message trough the form.