0.20.0

go-smtp v0.20.0

Brian Mayer (1):
      Remove DotLF to EOFState case

Simon Ser (10):
      client: don't check for nil Client.ext in SendMail
      client: add newline after validation in SendMail
      client: drop nil check from toSMTPErr
      Prefix SMTPError message
      Add defaultDialer
      Add TLS warning in Dial
      Remove host argument from NewClient
      Add SMTP smuggling test
      client: delay greeting
      client: drop Client.tls

guangwu (1):
      Fix typos