Docker-compose Mailgun

Has anyone an idea how email with Mailgun works on docker-compose??

mail__transport: ‘SMTP’
mail__from: ‘postmaster@ domain.tld’
mail__options__service: ‘mailgun’
mail__options__host: ‘smtp.eu.mailgun.org
mail__options__port: 465
mail__options__secure: ‘true’
mail__options__auth__user: ‘kontakt@domain.tld’
mail__options__auth__pass: ‘xxxxxxx’


2020-04-13 20:31:32] ERROR "POST /ghost/api/v3/admin/mail/test/" 500 10095ms

Failed to send email. Reason: Greeting never received.

"Please see https://ghost.org/docs/concepts/config/#mail for instructions on configuring email."

Error ID:
    c302ee80-7dc5-11ea-958a-97f45b5f5535

Error Code: 
    ETIMEDOUT

----------------------------------------

EmailError: Failed to send email. Reason: Greeting never received.
    at EmailError.GhostError (/var/lib/ghost/versions/3.12.1/core/server/lib/common/errors.js:10:26)
    at new EmailError (/var/lib/ghost/versions/3.12.1/core/server/lib/common/errors.js:34:20)
    at createMailError (/var/lib/ghost/versions/3.12.1/core/server/services/mail/GhostMailer.js:50:12)
    at MailComposer.returnCallback (/var/lib/ghost/versions/3.12.1/core/server/services/mail/GhostMailer.js:92:28)
    at SMTPConnectionPool._onConnectionError (/var/lib/ghost/versions/3.12.1/node_modules/simplesmtp/lib/pool.js:334:17)
    at SMTPClient.emit (events.js:311:20)
    at SMTPClient.EventEmitter.emit (domain.js:482:12)
    at SMTPClient.<anonymous> (/var/lib/ghost/versions/3.12.1/node_modules/simplesmtp/lib/client.js:293:18)
    at listOnTimeout (internal/timers.js:549:17)
    at processTimers (internal/timers.js:492:7)

Error: Greeting never received
    at SMTPClient.<anonymous> (/var/lib/ghost/versions/3.12.1/node_modules/simplesmtp/lib/client.js:289:25)
    at listOnTimeout (internal/timers.js:549:17)
    at processTimers (internal/timers.js:492:7)

But it won’t works.