Single opt-in adds new contacts to a mailing list after one sign-up step, without requiring confirmation. It removes friction from the signup process, enabling faster list growth and reducing drop-off from additional confirmation emails.
However, single opt-in can increase the likelihood of invalid or mistyped email addresses entering a database, which may negatively affect deliverability over time. Without a confirmation layer, marketers must rely on strong list hygiene, clear consent language, and ongoing engagement signals to maintain data quality.
When managed responsibly, single opt-in can support healthy audience growth, but many B2B teams balance it with complementary practices such as progressive profiling, lead scoring, and periodic re-engagement to ensure the list remains accurate and compliant with privacy expectations.