[CentOS] E-mail advice sought

[Alice Wonder]

On 04/30/2016 12:22 PM, Gordon Messmer wrote:
> On 04/30/2016 11:28 AM, Alice Wonder wrote:
>> Is there any advice on characters to allow in usernames?
> ...
>> 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?
>
> The RFC uses a list of allowed characters, and so must you.

For e-mail sent to people, yes.

But for what usernames are allowed when creating an account, I don't see 
why blacklisting characters that are not allowed in a username is a 
standards problem.