diff --git a/Doc/library/imaplib.rst b/Doc/library/imaplib.rst
index f1344ae9bb0a49..0a3754ae5c9adc 100644
--- a/Doc/library/imaplib.rst
+++ b/Doc/library/imaplib.rst
@@ -230,9 +230,19 @@ An :class:`IMAP4` instance has the following methods:
    that will be base64 encoded and sent to the server.  It should return
    ``None`` if the client abort response ``*`` should be sent instead.
 
+   Example of a SASL PLAIN *authobject*::
+
+      def plain_auth(data):
+         user = input('User: ')
+         password = getpass.getpass()
+         return f'{user}\x00{user}\x00{password}'
+
+      M.authenticate('PLAIN', plain_auth)
+
    .. versionchanged:: 3.5
       string usernames and passwords are now encoded to ``utf-8`` instead of
-      being limited to ASCII.
+      being limited to ASCII. :meth:`authenticate` is the only standard way
+      to use ``utf-8`` credentials on an ``IMAP4rev1`` server.
 
 
 .. method:: IMAP4.check()
@@ -638,4 +648,3 @@ retrieves and prints all messages::
        print('Message %s\n%s\n' % (num, data[0][1]))
    M.close()
    M.logout()
-