That might be some part of it but I doubt it. I suspect that it probably has to do with a network port that isn't exposed to the real world and/or that is being firewalled by Docker. The OP should please post the Dockerfile and docker-compose.yaml content.

In reply to Re^2: Net::SMTPS => auth no longer works - Migration from Debian to Docker container by Anonymous Monk
in thread Net::SMTPS => auth no longer works - Migration from Debian to Docker container by initB10r

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