Mail merge is a technique for sending a batch of emails where a base template is automatically populated with each recipient's individual details — name, company, role, and other fields — so every message is at least nominally customized.
Mail merge is a useful efficiency tool, but it's also where a lot of bad outreach comes from. Filling in a `{{first_name}}` and `{{company}}` field is not genuine personalization — the underlying message is still identical, and savvy decision-makers recognize a merged template immediately. Worse, broken merge fields ("Hi {{first_name}},") are an instant tell that destroys credibility.
Used well, mail merge handles the mechanical scaffolding so you can focus your energy on the genuinely custom part of each message. The principle from good job-search automation applies: automate the structure, but keep the meaningful personal hook human and specific to each recipient.