Senior Professional Services Engineer - OX App Suite (m/f/d)

Our mission:Are you an engineer with real technical depth AND do you want to own the relationship with one of our major hosting customer? Working through real production problems, translating operational needs into product improvements, and filling a role that matters to both sides? This combination is rare. At Open-Xchange (OX), we develop open-source communication and collaboration software used by public sector organizations, telcos, and hosting providers to keep data secure and under their control. Our products cover email, collaboration, DNS security, and related services, and are used by millions of people worldwide. Discover what OX offers you:We work in a non-hierarchical organization that empowers everyone to take responsibility, stay focused, and contribute directly to the company’s success and customer value.We value expertise and continuous professional development. Our professionals work closely with experienced colleagues, take ownership of their work, and continuously expand their skills.Openness and diversity are core to OX. Different perspectives, backgrounds, and ways of thinking strengthen our collaboration and help us see the bigger picture. Your team:You'll work in a dedicated cell built around one of our largest hosting customers - a provider running multiple brands on OX App Suite 8. Your closest collaborators are the Account Manager and Development Engineers, with Support looped in as needed. It's a largely independent seat, but you're one of several engineers across the company running the same model for other large accounts. Your new job:Be present in the customer relationship - regular calls, occasional on-site visits, and persistent continuity that the customer's technical teams know you by name and trust your word.Build reference labs and generate reference configurations from them.Participate in OX-internal development of those frameworks.Analyze and resolve technical issues across the OX App Suite 8 stack. As L1/L2 is sitting with our customer your role is escalation-facing (L2/L3) taking ownership from escalation through to resolution and keeping the customer informed throughout.Translate customer feature requests and operational requirements into clear input for internal product and development teams, and feedback internal constraints to the customer in terms they can act on.Support the customer through upgrades, configuration changes, and new feature rollouts. Document solutions, workarounds, and deployment specifics - both for the customer and internally - and leave things better documented than you found them. Formal on-call is not part of this role.A typical day mixes customer and internal calls, hands-on lab and reference-configuration work, and technical documentation - with occasional escalation support when a customer integration needs deeper troubleshooting.Limited travel is required for customer-facing meetings (~1-2 per quarter) and company-internal meetings (~1 per quarter). This is the tech stack you'll be working with:Scale 1-5 where 5 means “hands-on depth expected on day one” and 1 means “we expect nothing and train it on the job”:OX App Suite 8 | 1 |Kubernetes (Helm-based deployments) | 5 |Mail infrastructure: Dovecot (CE / Pro), Postfix, IMAP/SMTP) | 2 |Data layer: MariaDB, Redis | 3 |Storage: Object storage (S3-compatible), Rook Ceph | 2 |Identity: Keycloak, LDAP | 2 |Observability: Prometheus, Grafana (or comparable stack) | 3 |Tooling: Linux, Bash/Python, kubectl, Helm | 5 |Networking: Istio (operational awareness, not configuration ownership) | 2 | Your background:Proven ability to hold your ground in a technical disagreement with a customer or partner, and to stay composed and credible when a large account escalates - you can point to specific situations where you did this.Solid hands-on experience with Linux-based server environments.Working knowledge of several core stack components - mail infrastructure (IMAP/SMTP, Dovecot or equivalent).relational databases (Mari