What are the risks of contest/giveaway lists?

Contest and giveaway lists attract people who want to win something, not people who want to hear from you. That distinction matters for everything that follows.

The typical dynamic: you run a contest and collect email addresses as entries. People sign up to win. Many use a secondary email address or a disposable email service specifically for promotions and competitions. They have no interest in your brand beyond the prize. Once the contest ends, that relationship ends too.

The deliverability consequences show up in a predictable pattern. Initial opens are lower than normal because many participants do not check their contest entry email account regularly. Engagement drops sharply after the contest closes. Hard bounce rates rise as disposable addresses expire and secondary accounts go dormant. Complaint rates tend to be elevated because some participants are surprised to find they have been subscribed to a mailing list at all.

The legal angle: in jurisdictions under GDPR or CASL, the consent collected during a contest must be specific to your email program, clearly disclosed, and not bundled with the contest entry in a way that makes it a condition of participation. "You must subscribe to enter" is legally problematic in most EU member states.

If you have run a contest and want to keep using those addresses, treat the segment differently. Run a clear welcome sequence that establishes who you are. Monitor complaint rates closely on that segment. Suppress anyone who does not engage within 30 to 60 days. That is the fastest way to protect your sender reputation while making use of what you collected.

For the related risks of co-registration lists and rented lists, both share the same core issue: permission given in a context that does not translate to your ongoing email program.