diff --git a/maildump/smtp.py b/maildump/smtp.py
index 6f0043f..ed3586b 100644
--- a/maildump/smtp.py
+++ b/maildump/smtp.py
@@ -17,11 +17,11 @@ def __init__(self, server, conn, addr, smtp_auth):
         self._authorized = False
 
     def is_valid_user(self, auth_data):
-        auth_data_splitted = auth_data.split('\x00')
+        auth_data_splitted = auth_data.split(b'\x00')
         if len(auth_data_splitted) != 3:
             return False
 
-        if not auth_data.startswith('\x00') and auth_data_splitted[0] != auth_data_splitted[1]:
+        if not auth_data.startswith(b'\x00') and auth_data_splitted[0] != auth_data_splitted[1]:
             return False
 
         return self._smtp_auth.check_password(auth_data_splitted[1], auth_data_splitted[2])
@@ -30,17 +30,28 @@ def smtp_EHLO(self, arg):
         if not arg:
             self.push('501 Syntax: EHLO hostname')
             return
-        if self.__greeting:
+        # See issue #21783 for a discussion of this behavior.
+        if self.seen_greeting:
             self.push('503 Duplicate HELO/EHLO')
             return
-        self.__greeting = arg
-        self.push('250-%s' % self.__fqdn)
+        self._set_rset_state()
+        self.seen_greeting = arg
+        self.extended_smtp = True
+        self.push('250-%s' % self.fqdn)
         if self._smtp_auth:
             self.push('250-AUTH PLAIN')
+        if self.data_size_limit:
+            self.push('250-SIZE %s' % self.data_size_limit)
+            self.command_size_limits['MAIL'] += 26
+        if not self._decode_data:
+            self.push('250-8BITMIME')
+        if self.enable_SMTPUTF8:
+            self.push('250-SMTPUTF8')
+            self.command_size_limits['MAIL'] += 10
         self.push('250 HELP')
 
     def smtp_AUTH(self, arg):
-        print >> smtpd.DEBUGSTREAM, '===> AUTH', arg
+        print('auth:', arg, file=smtpd.DEBUGSTREAM)
         if not self._smtp_auth:
             self.push('501 Syntax: AUTH not enabled')
             return
@@ -97,7 +108,7 @@ def handle_accept(self):
         pair = self.accept()
         if pair is not None:
             conn, addr = pair
-            print >> smtpd.DEBUGSTREAM, 'Incoming connection from %s' % repr(addr)
+            print('Incoming connection from %s' % repr(addr), file=smtpd.DEBUGSTREAM)
             channel = SMTPChannel(self, conn, addr, self._smtp_auth)
 
     def process_message(self, peer, mailfrom, rcpttos, data, **kwargs):
diff --git a/maildump_runner/main.py b/maildump_runner/main.py
index 6082396..178b3c9 100644
--- a/maildump_runner/main.py
+++ b/maildump_runner/main.py
@@ -91,11 +91,19 @@ def main():
         args.htpasswd = os.path.abspath(args.htpasswd)
         print('Htpasswd path is relative, using {0}'.format(args.htpasswd))
 
+    if args.smtp_auth and not os.path.isabs(args.smtp_auth):
+        args.smtp_auth = os.path.abspath(args.smtp_auth)
+        print('SMTP Htpasswd path is relative, using {0}'.format(args.smtp_auth))
+
     # Check if the password file is valid
     if args.htpasswd and not os.path.isfile(args.htpasswd):
         print('Htpasswd file does not exist')
         sys.exit(1)
 
+    if args.smtp_auth and not os.path.isfile(args.smtp_auth):
+        print('SMTP Htpasswd file does not exist')
+        sys.exit(1)
+
     daemon_kw = {
         'monkey_greenlet_report': False,
         'signal_map': {signal.SIGTERM: terminate_server, signal.SIGINT: terminate_server},
@@ -137,7 +145,7 @@ def main():
 
         app.debug = args.debug
         app.config['MAILDUMP_HTPASSWD'] = None
-        if args.htpasswd:
+        if args.htpasswd or args.smtp_auth:
             # passlib is broken on py39, hence the local import
             # https://foss.heptapod.net/python-libs/passlib/-/issues/115
             try:
@@ -145,6 +153,8 @@ def main():
             except OSError:
                 print('Are you using Python 3.9? If yes, authentication is currently not available due to a bug.\n\n')
                 raise
+
+        if args.htpasswd:
             app.config['MAILDUMP_HTPASSWD'] = HtpasswdFile(args.htpasswd)
         app.config['MAILDUMP_NO_QUIT'] = args.no_quit
         smtp_auth = HtpasswdFile(args.smtp_auth) if args.smtp_auth else None