Can't send e-mails

I’ve set up Sentry using official Docker images, cron and workers are running properly with the same config as Sentry and my config.yml is:
mail.backend: ‘smtp’ ‘
mail.port: 465
mail.username: ‘xxx’
mail.password: ‘xxx’
mail.use-tls: true
These settings are visible on the /manage/status/mail page so I’ve run make build properly when I edited it. But when I try to send test e-mail, I get this error: Connection unexpectedly closed: timed out.
I’m using the same credentials on my GitLab instance so they must be correct. I have also allowed inbound and outbound traffic on port 465 in my firewall.

What should I do now?