I'm working on setting up an e-mail service.
I've got the e-mail servers working beautifully and am presently working on re-writing the parts of Roundcube I don't like (e.g. it uses inline JavaScript in a few places so CSP breaks it) but -
Is there any advice on characters to allow in usernames?
I know there are some wacky characters that are legal in e-mail addresses but are generally frowned upon - like
"very.(),:;<>[]".VERY."very@\ "very".unusual"@example.com
is apparently a legal address - but I know I don't want to allow ampersands and brackets etc. in an address.
I don't think a whitelist alphabet is best approach because of people with names that are not spelled with Latin characters.
Is there an existing blacklist of characters that technically legal but are generally avoided in e-mail addresses?
Thanks