Sisimai::Reason::UserUnknown - Bounce reason is "userunknown" or not.

       azumakuniyuki

"text()"
       text() method returns the fixed string "userunknown".

           print Sisimai::Reason::UserUnknown->text;  # userunknown

   "match(string)"
       match() method returns 1 if the argument matched with patterns defined in this class.

           print Sisimai::Reason::UserUnknown->match('550 5.1.1 Unknown User');   # 1

   "true(Sisimai::Fact)"
       true() method returns 1 if the bounce reason is "userunknown". The argument must be "Sisimai::Fact"
       object and this method is called only from "Sisimai::Reason" class.

       Copyright (C) 2014-2024 azumakuniyuki, All rights reserved.

       "Sisimai::Reason::UserUnknown" checks the bounce reason is "userunknown" or not.  This class is called
       only "Sisimai::Reason" class.

       This is the error that the local part (left hand side of "@" sign) of the recipient's email address does
       not exist. In many case, the user has changed the internet service provider, or has quit company, or the
       local part is misspelled. Sisimai will set "userunknown" to the reason of the email bounce if the value
       of "Status:" field in the bounce email is 5.1.1, or the connection was refused at SMTP "RCPT" command, or
       the contents of "Diagnostic-Code:" field represents that it is unknown user.

           <kijitora@example.co.jp>: host mx01.example.co.jp[192.0.2.8] said:
             550 5.1.1 Address rejected kijitora@example.co.jp (in reply to
             RCPT TO command)

       This software is distributed under The BSD 2-Clause License.

perl v5.40.1                                       2025-04-12                  Sisimai::Reason::UserUnknown(3pm)

       Sisimai::Reason::UserUnknown - Bounce reason is "userunknown" or not.

           use Sisimai::Reason::UserUnknown;
           print Sisimai::Reason::UserUnknown->match('550 5.1.1 Unknown User');   # 1