Senior ML Engineer - Email Security (remote work)

CloudLinux Inc.; Województwo mazowieckie; A distancia; PLN 180.000 - 320.000; Jornada completa

Ventajas ofrecidas por este puesto de trabajo

Fully remote

Paid vacation

National holidays

Unlimited sick leave

Private medical insurance

Co-working stipend

Education budget

Patent incentive

Descripción de la vacante

CloudLinux is a globally remote-first company building Imunify security products. We are replacing our rspamd-based spam filter with a transformer model running on customer CPUs, and we are seeking a Senior Machine Learning Engineer to drive development and production rollout of our email security tech.

You will ship detection models, build the Go-based inference engine, and own model quality end-to-end while collaborating with engineers.

Formación

• 5+ years shipping detection or classification systems where false positives have a cost you defended.
• You have taken at least one ML classifier to production yourself: corpus construction, threshold selection, error analysis.
• Hands-on transformer training in PyTorch: tokenizers, masked-language pre-training, fine-tuning, ONNX export, CPU inference measurement.
• Linux, shell, and Python on shared servers and a shared GPU.
• Daily usage of AI coding agents and tools.
• English at upper-Intermediate (B2) level or higher with strong written communication for docs, specs, and code reviews.

Responsabilidades

• Train, evaluate, and release spam-detection models: build corpus, set thresholds, review precision/recall.
• Build the production side of the new engine in Go: inference service, mail-filter integration, tokenizer, streaming parser.

Conocimientos

Detection systems

Production ML

PyTorch

Go/Rust

Python

Linux

Shell

ONNX

English (B2+)

Herramientas

Go

Rust

TensorFlow/ONNX

Descripción del empleo

CloudLinux is a global remote-first company. We are driven by our principles: do the right thing, employees first, we are remote first, and we deliver high-volume, low-cost Linux infrastructure and security products that help companies to increase the efficiency of their operations. Every person on our team supports each other and does what we can to ensure we all are successful.

Check out our website for more information: https://cloudlinux.com/

CloudLinux Inc. develops theImunify family of security products, designed to protect hosting environments from a wide range of cyber threats. One of these solutions is Imunify Email, an email security product that protects hosting servers against spam, phishing, and other email-based threats.

Imunify Email filters mail on about 5,000 hosting servers. Today the filter is rspamd with rules and a scoring model we train in-house. We are replacing it with a transformer we trained ourselves that runs on the customer's own CPU in under 100 MB and already beats rspamd at every operating point we measured. We are looking for a Senior Machine Learning Engineer to join our team and work alongside the engineer currently responsible for both the existing spam-filtering pipeline and the new ML model. Together, you will drive the development, improvement, and production rollout of our email security technology.

What you will do:

• Train, evaluate, and release spam-detection models: build the corpus, pick the threshold, read the precision/recall report, decide ship or retrain.
• Build the production side of the new engine in Go: the inference service, the mail-filter integration, the tokenizer, the streaming message parser.
• Fix detection quality end to end, from a customer's "this phishing got through" to a rule, a corpus fix, or a retrain, with the false-positive cost weighed against the catch.
• Keep the corpus tooling and training infrastructure running.
• Review and approve classifier, rule, and model changes, so no release waits on one person.
• Answer partner engineers who ask why a message scored the way it did.
• Write specs, handbooks, and post-mortems. That is how this team transfers knowledge.

Your first six months:

• Month 1: you ship a rule-model release on your own.
• Month 3: your first piece of the new engine is merged and running on staging.
• Month 6: a model release goes out while the principal engineer is away.

What you bring:

• 5+ years of shipping detection or classification systems where false positives have a cost you had to defend: anti-spam, anti-phishing, anti-malware, fraud, abuse.
• You have taken at least one ML classifier to production yourself: corpus construction, threshold selection, error analysis.
• Hands-on transformer training in PyTorch: tokenizers, masked-language pre-training, fine-tuning, ONNX export, CPU inference measurement.
• Linux, shell, and Python on shared servers and a shared GPU.
• Daily usage of AI coding agents and tools.
• English at upper-Intermediate (B2) level or higher, with particularly strong written communication skills for technical documentation, specifications, and code reviews. Your specs and merge-request descriptions count as much as your code.

It is a strong plus if you have:

• Email internals: SMTP, MIME, transfer encodings, SPF / DKIM / DMARC, how Exim, Postfix, and Dovecot handle mail to a filter.
• Experience in creating embedded models
• Go or Rustfor systems code: parsers, streaming, memory budgets, concurrency.
• rspamd or SpamAssassin internals: rules, composites, Lua plugins, mass-check scoring.
• Multi-million-sample corpora, labelling pipelines, annotator tooling.
• Small models for constrained hardware: quantization, distillation, latency budgets.
• LLM-based labelers or validators for scaling annotation.
• Hosting panels: cPanel, Plesk, DirectAdmin.

What's in it for you?

• A focus on professional development.
• Interesting and challenging projects.
• Fully remote work with flexible working hours, that allows you to schedule your day and work from any location worldwide.
• Paid 24 days of vacation per year, 10 days of national holidays, and unlimited sick leaves.
• Compensation for private medical insurance.
• Co-working and gym/sports reimbursement.
• Budget for education.
• The opportunity to receive a reward for the most innovative idea that the company can patent.

By applying for this position, you consent to the processing of your personal data as described in our Privacy Policy (https://cloudlinux.com/candidate-privacy-notice), which provides detailed information on how we maintain and handle your data.