Gmail: 530 5.5.1 Authentication Required. Learn more at

This Go program successfully sends email from my home computer, but on a virtual server on DigitalOcean receives the following error:

panic: 530 5.5.1 Authentication Required. Learn more at

Here's the code:

auth := smtp.PlainAuth("", "[email protected]", "PASSWORD", "smtp.gmail.com")
msg := "Subject: Hello\r\n\r\nWorld!"
e = smtp.SendMail("smtp.gmail.com:587", auth, "[email protected]", []string{email}, []byte(msg))
if e != nil { panic(e) }

Get to your Gmail account's security settings and set permissions for "Less secure apps" to Enabled. Worked for me.

Derp! I signed into the account and there was a "Suspicious login attempt" warning message at the top of the page. After clicking the warning and authorizing the access, everything works.

You need to go here https://security.google.com/settings/security/apppasswords

then select Gmail and then select device. then click on Generate. Simply Copy & Paste password which is generated by Google.