A lookalike domain is a domain that resembles another one, such as yourcompanyhq.com next to yourcompany.com. The term covers two very different uses.
Your own lookalikes
Cold emailers register variations of their own brand as secondary sending domains, so readers recognise the name while the main domain stays protected. That's normal and honest, as long as the emails say clearly who's sending.
Impersonation
The same technique is used by phishers to imitate other companies, for example swapping a letter (rn for m) or adding a word. Email security systems watch for domains that resemble well-known brands, especially new ones.
Choosing a good one
- Base it on your own brand, never on someone else's.
- Prefer short additions people read naturally: get, try, hq, team.
- Avoid tricks that look like typos; they read as phishing to filters and people alike.