Others may charge you membership or service fees for which the benefits are questionable, or which can be obtained elsewhere for free.
Still others claim the right to publish your entry whether or not you win a prize.
Similar to the online forums mentioned above, some of these self-publishing companies will sponsor "free" contests that are really lead-generation devices for aggressive marketing campaigns, or worse.
Copyright your manuscript before submitting, to reduce the risk of piracy.
Publishers in this category include: Famous Poets Society, Sparrowgrass Poetry Forum, The Amherst Society, The Poets' Guild, Poetry Press, Poetry Unlimited, The National Archives, and JMW Publishing.
Others try to sell you services, such as manuscript editing or agency representation.
We'd like to think so, but poetry books that aren't written by pop stars or ex-presidents rarely achieve that level of commercial success.
The total mismatch between these extravagant promises and the type of book being promoted makes us very suspicious of Airleaf's claim that "we have invited a very select group of authors and are accepting just the first 25." More likely they generated a letter like this for everyone on their mailing list who had a book out.
Some online contests require you to post an entire book-length manuscript for reader votes; this may prevent you from shopping the manuscript elsewhere if it does not win the contest, because it would already be considered "published".
Other contests assert the right to publish all entries without notice or compensation, which is not a good deal for writers and not a normal practice among reputable contests.