Total noob here but by browsing the sourcecode, I’ve found the function/regex that checks for the email correctness (permalink). I guess that by looking at the existing code and at the is_email_regex function, you can rather easily add an additional check to make sure the email is bound to the domain you want. No idea if this function/regex is the one the code actually tests email addresses against to check whether they are valid or not

Edit: apparently that function is not used in the registration process, but in the login one. I’m totally cluelessly wandering across the code so someone please correct me if I’m wrong. Apparently the registration process is handled here. I think that if you add an additional check on the email address here, you can obtain the result you’re looking for

Something like:

lazy_static! {
  static ref UNI_REGEX: Regex =
    Regex::new(r"^.+@somedomain$").unwrap();
}

pub fn is_uni_regex(test: &str) -> bool {
  UNI_REGEX.is_match(test)
}

and then in the file I linked above:

if !is_uni_regex(data.email) {
  return Err(APIError::err("unauthorized_email_domain").into());
}

…and you’d have to add a new unauthorized_email_domain key to the translations file. Again I hope I’m stressing it enough, do not trust me. There are probably more correct or consistent ways of doing it. I’m just trying to figure out by myself lol

Edit again: as far as I remember, Lemmy doesn’t send any verification url to the user email, so one could just make up an email address using the required domain and the account would be valid

Anyway yes, as AgreeableLandscape said, as long as you respect the AGPL license, you can do whatever you want to the public sourcecode, including adding this kind of verification

To my knowledge, no mechanism currently exists in the backend codebase that allow administrators to do that, but the code is open source so, for example, a university wanting to set up a member-only instance can implement an email restriction themselves.

The “correct” solution for this would be something like LDAP or similar (which any sysadmin would surely prefer over this manual account creation). We have an open issue for that, but we would probably need help to implement it.

the other answers cover it but do you have a university in mind to make a Lemmy instance for? that sounds cool