Contact import is the uploading of an existing database into an email tool. It is the step that most often causes lasting damage to a company's deliverability. There are three risks. Purchased or acquired lists for which there is no demonstrable legal basis are a breach of data protection rules, and they also contain traps set by providers to detect such practices. Old contacts collected years ago contain large numbers of non-existent addresses, and a high share of undelivered messages immediately lowers the sender's reputation. The third risk is uploading the entire database at once and sending the first campaign to everyone, which looks like typical spammer behaviour. The safe approach is to first verify and clean the database and send in stages, in smaller groups. It is not worth uploading contacts of unverifiable origin at all, because the damage will outweigh any short-term benefit.
See also: Contact list hygiene, Domain warming, Sender reputation.
