Senior ML Engineer - Email Security (remote work)

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About This Role

CloudLinux is seeking a Senior ML Engineer specializing in Email Security to join its global remote team. CloudLinux develops the Imunify product family, including Imunify Email, which filters mail across approximately 5,000 hosting servers to protect against phishing, spam, and other threats. In this position, you will work alongside the engineer currently handling the existing spam-filtering pipeline and the new machine learning model to drive the development, improvement, and production…

Job Description

Responsibilities

• Train, evaluate, and release spam-detection models by building corpora, choosing thresholds, reviewing precision and recall reports, and deciding whether to ship or retrain
• Build the production side of the new engine in Go, including the inference service, mail-filter integration, tokenizer, and streaming message parser
• Resolve detection quality issues end-to-end by implementing rules, fixing corpora, or retraining models while weighing false-positive costs against catch rates
• Maintain the corpus tooling and training infrastructure
• Review and approve classifier, rule, and model modifications
• Respond to inquiries from partner engineers regarding message scoring decisions
• Write specifications, handbooks, and post-mortems

Requirements

• 5+ years of experience shipping detection or classification systems such as anti-spam, anti-phishing, anti-malware, fraud, or abuse where false positives carry a cost
• Demonstrated experience taking at least one machine learning classifier to production, including corpus construction, threshold selection, and error analysis
• Hands-on transformer training experience using PyTorch, covering tokenizers, masked-language pre-training, fine-tuning, ONNX export, and CPU inference measurement
• Proficiency with Linux, shell scripting, and Python on shared servers and shared GPUs
• Daily usage of AI coding agents and tools
• Upper-Intermediate B2 English level or higher with strong written communication skills for technical documentation, specifications, and code reviews

Qualifications

• Knowledge of email internals such as SMTP, MIME, transfer encodings, SPF, DKIM, DMARC, and how Exim, Postfix, and Dovecot handle mail
• Experience creating embedded models
• Proficiency in Go or Rust for systems code including parsers, streaming, memory budgets, and concurrency
• Familiarity with rspamd or SpamAssassin internals including rules, composites, Lua plugins, and mass-check scoring
• Experience with multi-million-sample corpora, labelling pipelines, and annotator tooling
• Experience building small models for constrained hardware involving quantization, distillation, and latency budgets
• Familiarity with LLM-based labelers or validators for scaling annotation
• Experience with hosting panels such as cPanel, Plesk, and DirectAdmin

Core Skills

Benefits

• Fully remote work with flexible working hours
• 24 days of paid vacation per year
• 10 days of national holidays
• Unlimited sick leaves
• Compensation for private medical insurance
• Co-working and gym or sports reimbursement
• Budget for education
• Opportunity to receive a reward for patentable innovative ideas

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