Outbound Glossary
Data residency
Which country your data physically sits in. For most outbound tools the honest answer is the United States, and almost nobody checks.
Data residency is where data is stored and processed, as opposed to where the company selling you the tool is registered. Some providers offer an EU region, some offer it only on higher plans, and some do not offer it at all.
It matters for two reasons. Transfers out of the EU need a legal basis and documentation, and some buyers, especially in regulated industries and the public sector, will simply refuse a vendor who cannot answer the question. If you run outbound for European companies, knowing the answer per tool is a commercial advantage, not just a compliance chore.
Why residency and compliance are different questions, and what each one actually buys you with a buyer, is in cold email and GDPR in Europe.