Always use TLS when sending email
Email filtering by ISP today is very bad, returning 250 2.0.0 OK but actually no email was sent, your email is lost. Also someone can read your email when sent How do you know if your email has been filtered or not? try telnet to the external smtp server port 25, the normal response should be like this: And when filtered, response like this: See, there are no STARTTLS in the filtered network, so the e-mail client is forced to send in plain text, unencrypted. Not only email clients, but also applications that send notifications via email Tips: Use other SMTP port like 587, 465 Always use TLS in your mail client SMTP setting: STARTTLS or SSL/TLS