Process agent
What is a process agent?
The rules of English civil procedure require process of legal proceeding before an English (or Welsh) Court to be served in England or Wales (or, at the limit, in adjacent territorial waters). Note: service in Scotland will not do. This means you can serve process on someone rowing a boat in the Bristol Channel, but not in Glasgow.
A process agent is a business located England or Wales (or, in theory, adjacent territorial waters) which accepts service of legal proceedings filed in English courts on behalf of a person who has no place of business in England or Wales.
New York
The New York rules of civil procedure do not require service of process within the state of New York, nor even her territorial waters. Your process service guy can travel far and wide, serving the miscreant in whichever jurisdiction he may find an authorised representative to whom he can hand the papers. As long as he trots back and files an affidavit of service in the New York court, that will do. Therefore - however much money CT Corporation may reap persuading its offshore clients otherwise, foreigners conducting their affairs under the laws of the state of New York need not appoint a NY process agent.
Who needs one?
Any counterparty who does not have a permanent place of business in England or Wales. Process agents are standard in English law contracts with overseas counterparties.