On 2026-09-25, Gustavo Rios <[email protected]> wrote: > --00000000000068870c065c51c5b4 > Content-Type: text/plain; charset="UTF-8" > > Hi folks! > > I am trying to implement a small program on my server e i am in need to > know what is a alivade DNS string (FQDN); and about email, what is a valid > email address ?]
you are in for a world of pain if you want to correctly validate email addresses. many things which you might assume are invalid, are actually valid. it is even validate to include whitespace, for example, as long as it's escaped properly. fqdn is simpler, but there are still gotchas with internationalised domain names, etc. look for existing libraries for your preferred programming language to do validation rather than rolling your own, there are many, though be prepared for them to not be completely correct either (but probably much better than most people will manage themselves on initial attempts). for an example of "world of pain" see https://stackoverflow.com/questions/13992403/regex-validation-of-email-addresses-according-to-rfc5321-rfc5322 (but that doesn't handle non-ascii) -- Please keep replies on the mailing list.
