Senior Machine Learning Engineer (Email Security)

Location: Remote; listed locations include Warsaw, Poland; Sofia, Bulgaria; Podgorica, Montenegro; Tbilisi, Georgia; Yerevan, Armenia; and Madrid, Spain. The role can be performed from any location worldwide with flexible working hours.

Company

hirify.global develops Linux infrastructure and cybersecurity products, including Imunify Email, which protects hosting servers against spam, phishing, and other email-based threats.

What you will do

• Train, evaluate, release, and improve spam-detection models, including corpus construction, threshold selection, precision/recall analysis, and retraining decisions.
• Build the production engine in Go, including the inference service, mail-filter integration, tokenizer, and streaming message parser.
• Investigate detection-quality issues from customer reports through rules, corpus changes, and model retraining while balancing false positives against detection rates.
• Maintain corpus tooling and training infrastructure, and review classifier, rule, and model changes.
• Support partner engineers by explaining message scores and document technical decisions through specifications, handbooks, and post-mortems.
• Within the first six months, independently ship a rule-model release, merge and stage a component of the new engine, and release a model while the principal engineer is away.

Requirements

• 5+ years of experience shipping detection or classification systems where false positives had a measurable cost, such as anti-spam, anti-phishing, anti-malware, fraud, or abuse systems.
• Experience taking at least one ML classifier to production independently, including corpus construction, threshold selection, and error analysis.
• Hands-on transformer training in PyTorch, including tokenizers, masked-language pre-training, fine-tuning, ONNX export, and CPU inference measurement.
• Experience using Linux, shell, and Python on shared servers and a shared GPU.
• Daily use of AI coding agents and tools.
• English at upper-intermediate (B2) level or higher, with strong written communication skills for technical documentation, specifications, and code reviews.

Nice to have

• Email internals, including SMTP, MIME, transfer encodings, SPF, DKIM, DMARC, and mail handling by Exim, Postfix, and Dovecot.
• Experience creating embedded models.
• Go or Rust systems programming involving parsers, streaming, memory budgets, or concurrency.
• 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, including quantization, distillation, and latency budgets.
• Experience with LLM-based labelers or validators for scaling annotation.
• Experience with hosting panels such as cPanel, Plesk, or DirectAdmin.

Culture & Benefits

• Remote-first work with flexible working hours and worldwide location flexibility.
• 24 paid vacation days per year, 10 national holidays, and unlimited sick leave.
• Compensation for private medical insurance.
• Co-working and gym or sports reimbursement.
• Professional development focus and an education budget.
• Opportunity to receive a reward for an innovative idea that the company can patent.