Email not Working in Rocketchat

Description:

rocketchat to version 4.6.3 can not send e-mails

Steps to reproduce:

Try to send any notification or other e-mail message

Expected behavior:
E-mails are sent

Actual behavior:

E-mails are not sent

Server Setup Information:

Version of Rocket.Chat Server: 4.6.3
Operating System: Linux
Deployment Method: docker
Number of Running Instances: 1
Client Setup Information
Desktop App or Browser Version: Chrome
Operating System: Windows 10

Relevant logs:

Exception in defer callback: Error: Greeting never received
at SMTPConnection._formatError (/app/bundle/programs/server/npm/node_modules/meteor/email/node_modules/nodemailer/lib/smtp-connection/index.js:784:19) at SMTPConnection._onError (/app/bundle/programs/server/npm/node_modules/meteor/email/node_modules/nodemailer/lib/smtp-connection/index.js:770:20)
at Timeout. (/app/bundle/programs/server/npm/node_modules/meteor/email/node_modules/nodemailer/lib/smtp-connection/index.js:704:22)
at listOnTimeout (internal/timers.js:557:17)
at processTimers (internal/timers.js:500:7) { code: ‘ETIMEDOUT’, command: ‘CONN’ }