PECR (the Privacy and Electronic Communications Regulations) are the UK's rules for electronic marketing, alongside UK GDPR. They decide when you may send marketing email without consent.
The key distinction
- Corporate subscribers (limited companies, LLPs, public bodies, including an employee's work address there): you may send marketing email without prior consent, as long as you say who you are and give an easy way to opt out.
- Individual subscribers (consumers, and sole traders and some partnerships): you need consent, with a narrow exception for your own existing customers.
GDPR still applies
Even where PECR allows the email, processing a named person's work address is personal data under UK GDPR. Cold B2B email usually relies on legitimate interest, which means telling people where you got their details and honouring objections at once.
For cold email to the UK
Email people at companies, about something relevant to their role, say who you are, explain how to opt out and keep a suppression list. Avoid sole traders without consent. This isn't legal advice.