Yet another Hacker News

Show HN: I wrote an email app that accepts only one sender per inbox

28 points edpin2000 2 hours ago 27 comments

Infinite inboxes, including prefixes where you don't have to create inboxes before you use them -- they self create when you add a suffix.

Three types of inboxes: - One sender. Locks to the first domain to send email (except gmail, outlook, etc where it locks to an email account for obivous reasons. It bounces everyone else. - Temporary. Lasts for a while (24h, 7days, etc) then bounces. Received messages stay or go as per your choice. - Prefix. The most powerful. Declare a prefix like "service" and then invent any suffix, like "service-netflix" or "service$bank" and it creates a new one-sender inbox locked to whoever wrote first.

Bring you own domain. Bring your own AI (MCP server ready). Forwarding.

Please help me test it.

cloudmanic 2 hours ago | parent

I have used this service since I found it on product hunt. I am loving it! My inbox is way cleaner now.

edpin2000 1 hour ago | parent

Glad to know it's working for you!

hmokiguess 1 hour ago | parent

This is amazing, my dream has always been that outlook, gmail, and the likes allowed for setting up bounce rules.

edpin2000 1 hour ago | parent

Yes! And it can bounce/block any sender and entire domains too (across all your inboxes, if you choose).

jlm66 1 hour ago | parent

Email, snail mail, text messages etc. all need, IMO, options for ONLY allowing incoming messages from known sources. This seems like it is really aiming to do that for Email and I applaud the effort. Hopefully, it will take off in a big, big way.

asdff 1 hour ago | parent

Email at least you can set this up with a rule that checks the sender against your contacts and throws them into some folder.

edpin2000 41 minutes ago | parent

True. I find setting up rules and adding to contacts adds work to my day-to-day though. I'm hoping to make something simple and seamless. Prefix inboxes are as simple as I could think so far: make one up, add a suffix on the spot when you handout an email address -- boom, locked to the first one who uses it.

edpin2000 43 minutes ago | parent

I hope so too. I hope I have the right set of features so far. Happy to hear thoughts and early feedback.

mkirsten 1 hour ago | parent

Nice and looks helpful. It’s crazy when you think about it - email is so prevalent in our lives, yet the scope of innovation last 20 years is that we can react to an emails with emojis.

edpin2000 44 minutes ago | parent

That's so true. Gmail used to be cool, now it's old and clunky and their "unsubscribe" feature does not do that reliably. I want to tackle that next, look at domains that continue to email people after they unsubscribe.

mahboi 17 minutes ago | parent

If anyone is reacting to my emails, I'm not seeing it, might be some vendor-specific thing. Which is fine, I don't want that.

What I really want is for unauthenticated senders to be reliably blocked. Even Gmail/Gsuite will allow spoofed emails from the same domain, though it may flag them as spam. I get that there are special circumstances where a legitimate sender can't authenticate itself, but you know what, I don't need ghetto servers emailing me.

xlii 44 minutes ago | parent

I think I'm missing something but I've have an option to use <anything>@<ident>.domain.com for couple years now.

I don't find it that useful though and usually go with standard alias i.e. user+<anything>@domain.com

As for single sender locking - not sure how useful that is. I mean you can get github.com email or notifications.github.com so you miss half of them?

edpin2000 37 minutes ago | parent

On the "+" sign comment: I find that many spammers already know the trick. That's why I built a prefix where any suffix will work. If you have "turtle" as a prefix, you can add "turtle$bank", "turtle-barber", etc on the spot, without having to create each suffix.

As for single sender, we attach to the domain, so *.github.com would be allowed. The main problem, to be honest, is when email comes from apple.com, icloud.com, applehq.com, etc. I'm considering a power-feature where you could pre-select a few domains or allow all and then lock it. I feel it would be best for power users only. What do you think?

amflare 37 minutes ago | parent

You can already do this with any normal email account. Just do myemail+whatever@domain.com. You can put anything you want behind the +, and it still works. i.e. myemail+chase@domain.com, myemail+huffpost@domain.com, myemail+facebook@domain.com.

This used to be used as some sort of automatic labeling system that was supposed to be part of the spec eons ago, but it works just fine for generating unique emails so that you can see if/when an email has been leaked.

_djo_ 23 minutes ago | parent

I assume spammers have become adept at stripping anything between + and @ in email addresses, so this isn't as reliable as properly masked addresses.

edpin2000 14 minutes ago | parent

That's been my experience too. That's why prefix inboxes allow any suffix, including "-", "_", "$", "!" etc.

bch 10 minutes ago | parent

The “x+tag@domain.com” format is also rejected by many validators, sadly. I thought this was a gmail feature, but was corrected[0][1] a while ago.

[0] https://www.rfc-editor.org/rfc/rfc5233

[1] https://news.ycombinator.com/item?id=43952475

DoctorOW 22 minutes ago | parent

I think the benefit is supposed to be the locking feature. Any human that sees myemail+chase@domain.com and wants to circumvent your filters to get to your main inbox (typically for sales purposes) can figure out to email myemail@domain.com. With this product, the email is undeliverable unless they label their emails correctly.

edpin2000 15 minutes ago | parent

Exactly. Even bots can strip the "+" and bombard you with junk. With a prefix inbox you can invent any suffix. I have a "service" prefix that I add suffixes to it when I need: "service-netflix", "service$bank", "service.newsletter-1". I don't need to pre-create each one, only "service" is enough and then any suffix locks to the sender. They can't sell your email. And they may never know to invent a new suffix because they don't know where the prefix starts. You can make it "sdfawetr" if you want.

drayfield 35 minutes ago | parent

For context I'm sleep deprived so sorry if I've missed something obvious, but what differentiates this with something like Fastmail's masked email offering? I use unique emails for every service I use and it works beautifully. This seems... more complicated? I under there's a price difference, but little else.

tmarice 29 minutes ago | parent

I recently found out there is a limit to the number of masked emails you can have on Fastmail (1000, iirc -- definitely not infinite for practical purposes). Also, I miss the option of being able to create masked emails on all the domains I connected to Fastmail -- you can only use the "main" one.

edpin2000 18 minutes ago | parent

It aims to be simpler. It's not a mask. It has forwarding as an option but the idea is that you can use one of the inbox types for different needs. The one I use the most is prefix, because you create it once and then you can tack on any suffix to it. When the first sender reaches you, that suffix become locked to their domain (or account, if it's a gmail, outlook, yahoo, etc). That seems pretty useful for subscriptions. For one-time codes, just create a temporary one every so often. It has the option to delete itself (and optionally take the email with it).

ssivark 17 minutes ago | parent

Masked emails are infinitely shareable eg. a spammer can harvest that email address and then reach you. You don't typically have a setting to block anyone else (other than the original intended counter-party) from reaching you -- unless you set up some specific filtering rule (if that's even supported).

ssivark 25 minutes ago | parent

Nice idea! JFYI, in case you ever run into design questions when extending this, you seem to be implementing a version of Object Capabilities (specifically revocable forwarders / caretaker pattern), specialized for the SMTP situation -- as you want to share with someone the capability to send you messages, but you want that capability to not be shared recursively.

Since you're also thinking about a user giving their agent access to their inbox -- any thoughts on what are the right capability primitives for that situation, and how the API & access tokens can represent that?

edpin2000 11 minutes ago | parent

Agents can create new inboxes and inboxes can be of 3 types, besides "Permanent" which is just a regular inbox. The other types don't have "rules" that you can customize. Instead the rules are baked-in: Temporary -> expires after some time, One-sender: allows only one sender (the first one to prove its email identity), Prefix: similar to one-sender but creates a new inbox for every suffix (and if spammers catch on to the prefix, you can delete it and create a new one).

zatkin 1 minute ago | parent

How does it handle the scenario where the sender changes the domain they originate from? It may seem a bit unusual, like when a company rebrands (think of like Facebook originally sending from facebook.com, but then sending from meta.com later on).

another-dave 30 seconds ago | parent

this sounds really clever.

One suggestion - external contacts won't know that this address will bounce for anyone they add in CC. Maybe have an option where if I include the original whitelisted domain/person in the chain then it will let the mail through even if it's from a non-whitelisted person.

Just thinking of scenarios like, you give out your email address to <your-neighbour@gmail.com> who then emails you about a 5-a-side game with a few friends but any messages from any of the other friends bounce.

Or you apply for a job at ACME Inc and then you get a message back from `alice@acme.com` saying, please coordinate with `bob@our-recruiter-consultancy.com` who'll arrange the interview but Bob can't contact you