Bitbucket mail setting STARTTLS

[YOTHA]

Dear

My setting require STARTTLS and bitbucket can't send an email of test how I can set this STARTTLS ?

[Gonchik Tsymzhitov]

Dear Youtha, 
if you open  server_name /admin/mail-server
You can see checkbox 'Use SSL/TLS if available:'
             
Just enable and please set correct number of port. 
I am using on Bitbucket v5.3.2, it works well.
  
Cheers,
Tsymzhitov Gonchik