Re: How do I check if the format of an email address is valid?

[Lennart Borgman]

Reiner Steib wrote:
> Is anyone aware of any missing TLDs?
>
> (defcustom message-valid-fqdn-regexp
>   (concat "[a-z0-9][-.a-z0-9]+\\." ;; [hostname.subdomain.]domain.
>           ;; valid TLDs:
>           "\\([a-z][a-z]" ;; two letter country TDLs
>           "\\|biz\\|com\\|edu\\|gov\\|int\\|mil\\|net\\|org"
>           "\\|aero\\|coop\\|info\\|name\\|museum"
>           "\\|arpa\\|pro\\|uucp\\|bitnet\\|bofh" ;; old style?
>           "\\)")
>   "Regular expression that matches a valid FQDN."
>   ;; see also: gnus-button-valid-fqdn-regexp
>   :version "22.1"
>   :group 'message-headers
>   :type 'regexp)
>      
>   
> > > You can customize the variable!
> > >       
>
> BTW, the tin newsreader even hard-codes a matrix of (in)valid
> two letter country domains. The user/admin has to recompile to add new
> domains.  IIRC it's used when checking for a valid FQDN.
>
>   
> > This argument can be used in the reverse direction too. Do most
> > users really gain something from the list of known TLD:s in the
> > regexp?
> >     
>
> For the purpose in Gnus: Yes, IMHO.  What would you suggest to use
> instead?
>   
Why not just [a-z]{2, 6}

> > I just want to check the format of email addresses entered on a html page.
> >     
>
> And you'll post-process it using Emacs?
>   
Just what the user entered (in completion in nxhtml-mode).

> I wasn't joking. :-)  Of course not from the format, but...
>
> Basically you need to do something like "host -t mx" (using
> `dig.el'?), connect to the smtp port, send "RCPT TO:" and parse the
> output ("user unknown"?).  But I'm not sure if this still works
> nowadays.
>
> Bye, Reiner.
>   
Thanks, I did not know. But that seems out of the scope for me right 
now. (And it is a bit complicated to find the tools on w32 - but they 
seem to be in BIND.)