luceos masihdindar Why this extension using swiftmailer that it's abandoned already? Laravel uses swiftmailer, newer versions don't. Flarum simply re-uses that code. This extension re-uses Flarums' code. The error is due to a misconfiguration in your settings not because swiftmailer is deprecated. Please stick to your primary discussion: https://discuss.flarum.org/d/31168-error-in-swiftmailer-my-website-cant-send-emails
