SMTP Authentication Support module error?

Question

Drupal

Tell me plz! I use the SMTP Authentication Support module when sending a test email, it gives an error:
Notice: Undefined variable: to in SmtpMailSystem->mail() (line 53 of /home/site.ru/docs/sites/all/modules/smtp/smtp.mail .inc).
I don’t understand what’s the matter, I searched the Internet, I didn’t find the answer! Tell me please.