EasyNetQ by Mike Hadlow,Michael Denny,Yury Pliner,Wiebe Tijsma,Contributors (see GitHub repo)

<PackageReference Include="EasyNetQ" Version="8.0.0-alpha6" />

.NET API 650,240 bytes

 DeadLetterStrategy

public static class DeadLetterStrategy
Represents dead letter strategies of a queue
public const string AtLeastOnce = "at-least-once"

Messages are re-published with publisher confirms turned on internally.

public const string AtMostOnce = "at-most-once"

Default one for quorum queues. Messages are removed from the original queue immediately after publishing to the DLX target queue. This ensures that there is no chance of excessive message buildup that could exhaust broker resources, but messages can be lost if the target queue isn't available to accept messages.