On 15 Aug 2020, at 7:04, Mark W. Datysgeld wrote:

So, like many UASG discussions, this is very enlightening from an 
academic point of view. However, my question after all of these 
considerations is: what are the reasonable next steps to take in 
relation to making this into some sort of guideline that we can 
recommend to third parties who need a simple answer?

The recommendation I made during the Java tutorial on UA is as follows:
- use a simple regex to throw out the basic errors (example: an (EAI 
email address must have a « @ «  and at least one « . » on the 
right side; you can enhance this a bit, but if you go too much, then you 
start getting into trouble)
- use a library for verifying IDNA.
- there is not that much one can do on the left side of an EAI email 
address. maybe just verifying it is a valid UTF-8 string.

John Levine also wrote similarly in a previous email in this thread.

Marc.

 PS: There are 3 very active Marks/Marc on this group, so I'd suggest 
 the list always use the first letter of our surnames to make it less 
 confusing.

 Regards,
 -- 
 Mark W. Datysgeld from Governance Primer [www.markwd.website]
 In partnership with AR-TARC and the Brazilian Association of Software 
 Companies (ABES)

 On August 14, 2020 3:33:08 PM GMT-03:00, Arnt Gulbrandsen 
 <arnt@gulbrandsen.priv.no> wrote:
 Writing a single regexp is probably forbiddingly complicated (and I 
 say

 that as someone who once wrote a 25-line regexp and used it in
 production), but writing two might work well.

 One that accepts most
 valid names and accepts noting invalid, and one that rejects
 common/assumedly common errors and accepts everything that's valid 
 (and

 some errors). These should be simple to write, and yield three 
 answers:

 good, bad and uncertain.

 Arnt
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