I have issues with easy appointments and WP mail SMTP (used to avoid spam). Sometimes confirmation mail are not sent and I get several different errors from time to time. In addition to the ones below once I got also an error that I exceeded the number of mails per hour from the same IP address (using ovh mail). Please help. If I can resolve the issue I will upgrade to Pro.  TYPE: MAIL
ERRORS: {"wp_mail_failed":["The following From address failed: prenotazioni@eugeniomagni.it : MAIL FROM command failed,Error: nested MAIL command\r\n,503,5.5.1SMTP server error: MAIL FROM command failed Detail: Error: nested MAIL command\r\n SMTP code: 503 Additional SMTP info: 5.5.1"]} TYPE: MAIL
ERRORS: {"wp_mail_failed":["SMTP Error: data not accepted."]}