Hi @hotmeatballsoup, the transport strategy should be enough, no need for those extra properties. I have tested the following with success:

final mail email = new Email();
email.setFromAddress("lollypop", "[email protected]");
email.addRecipient("C.Cane", "[email protected]", RecipientType.TO);
email.setText("We should meet up!");
email.setTextHTML("<b>We should meet up!</b>");
email.setSubject("hey");

new Mailer("smtp.gmail.com", 25, "your user", "your password", TransportStrategy.SMTP_TLS).sendMail(email);
new Mailer("smtp.gmail.com", 587, "your user", "your password", TransportStrategy.SMTP_TLS).sendMail(email);
new Mailer("smtp.gmail.com", 465, "your user", "your password", TransportStrategy.SMTP_SSL).sendMail(email);

Possible causes:

You have two-factor authentication enabled in gmail, in which case you need to generate an application-specific password for your test (Google App Passwords)

Your credentials are not entered correctly (if I remember correctly, you should use your username, not your email (eg. your.user instead of [email protected])). I'm currently behind a proxy myself, so I can't test it right now.

You are behind a proxy and the proxy is blocking you (but the exception doesn't seem to match this situation)

A router is blocking the outgoing ports (but again, the exception doesn't match)

Some other network issue

Simple Java Mail is very simple in regards to networking details, meaning the problem is most likely outside the library. You can enable debug logging for some more info, it might help shed some extra light on the exception (mailer.setDebug(true)).

from simple-java-mail.