It takes very long for smtp.exmail.qq.com to return if credentials are incorrect.

[reasonerjt]

With current code if the mail server is set to
host: smtp.exmail.qq.com
port: 465
ssl: true

And when the credential is incorrect, the function sendMailWithTLS takes 1 minute to return.

Per investigation seems smtp package does not work very well with this mail server.
An issue has been opened to golang to track:
golang/go#18094

We don't plan to hack go's library to workaround this issue at least for 0.5.0.

[frankli0614]

@reasonerjt the port should be 465.

[reasonerjt]

thanks @frankli0614