Choosing Inbox Relays
When you first set up your Nostr account, the client that you opt to use will assign you default relays to manage responses to your posts. One part of these defaults are inbox relays, sometimes referred to as "read" relays. This is where all of the likes, replies, and any other activity on your notes will be sent for you to see. Most default relays are free to connect with and may send you incoming interactions from anyone. This setup allows for new people to chat and interact with ease until they can navigate their way around Nostr more efficiently. It also means that your notes may be more open to receiving spam replies. Most free-to-the-public relays try their best to mitigate spam but it is often difficult to determine whether a note is from a spammy bot or a real human until that user has either established some history or otherwise proven themselves to be legitimate through methods like reputation building, paying a fee, or providing proof-of-work computations. If and when the time comes that your notes become the target of a spammer, it is surely time to adjust your public inbox relay connections. Doing so beforehand can prevent annoying and possibly uncomfortable situations from effecting your Nostr experience.
A good inbox relay that is easy to set up and understand will often charge a small connection fee. These relays will use more aggressive methods of spam control and often will provide other services alongside of that feature. You may find one that also offers DM services, search functionality, or NIP-05 addresses. There are one-time fee relays, as well as subscription services that will offer higher levels of features and customer support. This is the first and simplest suggestion for tailoring your relay list to match your needs.
Once you have established some history within Nostr and develop a personal network, you are able to consider switching your inbox relay connections to WoT relays. These relays are operated by someone who acts as the center point of trust, which in this case means a person with a contact list of people that they deem to be legitimate people. From there, permission to receive incoming interactions branches out to who they follow, who their followers' follows, and sometime further. The degree is chosen and set by the relay operator. These relays are an incredibly effective option for reducing spam, though on occasion an individual within the web may unknowingly follow an account that many others consider to be spammy. You can find more information about Web of Trust relays, including how to operate your own in this post.
Allow list or "whitelist" relays keep a list of who is approved to write notes to the relay. Connecting to an allow list relay can greatly limit who is able to send you replies and other interactions. This may be desirable, if you wish to limit who is able to talk directly to you. As with any of these options, people may be replying through other relays & those replies may be visible to anyone who is "reading" from them. You are simply not seeing it. These allow list relays may charge a fee, as well as require other criteria based on behavior and posting habits, in order to maintain the right conversate on that relay.
Another option is a personal relay, for which you control all incoming content based on the criteria that you choose. Hosted relay services and various relay software packages are available for you to use. This may the best and ideal option for managing incoming replies, though it is technically more complicated and not something that new users will likely be equipped to handle very easily, unless they have come to Nostr with previous self-hosting experience.
Other inbox relay implementations are under development. This post may be updated with noteworthy information in the future. For a great introduction to relay management, check out this video. To explore what different relays have to offer, visit https://nostr.watch .