I'm building a website using Django. The website could have a significant number of users from non-English speaking countries.
I just want to know if there are any technical restrictions on what types of characters an email address could contain.
Are email addresses only allowed to contain English letters, numbers, _, @ and .?
Are they allowed to contain non-English alphabets like é or ü?
Are they allowed to contain Chinese or Japanese or other Unicode characters?
I took a look at the regex in pooh17's answer and noticed it allows the local part to be greater than 64 characters if separated by periods (it just checked the bit before the first period is less than 64 characters). You can make use of positive lookahead to improve this, here's my suggestion if you're really wanting a regex for this
^(((?=.{1,64}@)[^<>()[\].,;:\s@"]+(\.[^<>()[\].,;:\s@"]+)*)|((?=.{1,66}@)".+"))@(?=.{1,255}$)(\[(IPv6:)?[\dA-Fa-f:.]+]|(?!.*?\.\.)(([^\s!"#$%&'()*+,./:;<=>?@[\]^_`{|}~]+\.?)+[^\s!"#$%&'()*+,./:;<=>?@[\]^_`{|}~]{2,}))$
Building on @Matas Vaitkevicius' answer: I've fixed up the regex some more in Python, to have it match valid email addresses as defined on this page and this page of wikipedia, using that awesome regex101 website: https://regex101.com/r/uP2oL7/26
^(([^<>()\[\]\.,;:\s@\"]{1,64}(\.[^<>()\[\]\.,;:\s@\"]+)*)|(\".+\"))@\[*(?!.*?\.\.)(([^<>()[\]\.,;\s@\"]+\.?)+[^<>()[\]\.,;\s@\"]{2,})\]?
Hope this helps someone!:)