title_body: How are transaction fees determined for bulk sends? I have a use case where I want to send to many addresses on a regular basis.
  Let's say I want to send to 1 million addresses. I've read that Cardano enforces a &quot;minimum transaction fee.&quot; But is this fee applied to each recipient address in a bulk transaction? Or is it for the overall transaction?
  If it's the case where I pay a fixed fee per bulk send, what is the maximum number of addresses I can send to in one bulk transaction?
upvoted_answer: The minimum fee is for the transaction as a whole, calculated as a * size(tx) + b, where a and b are protocol parameters. However, there is a Min-Ada-Value of 1 ADA which is the minimum size of a UTxO. The maximum possible UTxO set of Cardano is actually 45 billion for this reason. Anyway, you'd need to send 1 ADA per UTxO (which can be in the same transaction) and then the only limit should be the size of the transaction being less than the size limit of a block.
  You can read more about this here:
  Docs:
  https://cardano-ledger.readthedocs.io/en/latest/explanations/min-utxo.html
  Implementation:
  https://github.com/input-output-hk/cardano-ledger-specs/blob/master/shelley-ma/impl/src/Cardano/Ledger/ShelleyMA/Rules/Utxo.hs