diff --git a/config/filter.d/sendmail-auth.conf b/config/filter.d/sendmail-auth.conf
index de1f8e36..3fa3c701 100644
--- a/config/filter.d/sendmail-auth.conf
+++ b/config/filter.d/sendmail-auth.conf
@@ -15,7 +15,7 @@ addr = (?:IPv6:<IP6>|<IP4>)
 prefregex = ^<F-MLFID>%(__prefix_line)s</F-MLFID><F-CONTENT>.+</F-CONTENT>$
 
 failregex = ^(\S+ )?\[%(addr)s\]( \(may be forged\))?: possible SMTP attack: command=AUTH, count=\d+$
-            ^AUTH failure \([^\)]+\):(?: [^:]+:)? (?:authentication failure|user not found): [^,]*, user=<F-USER>(?:\S+|.*?)</F-USER>, relay=(?:\S+ )?\[%(addr)s\](?: \(may be forged\))?$
+            ^AUTH failure \([^\)]+\):(?: [^:]+:)? (?:authentication failure|user not found): [^,]*, (?:user=<F-USER>(?:\S+|.*?)</F-USER>, )?relay=(?:\S+ )?\[%(addr)s\](?: \(may be forged\))?$
 ignoreregex =
 
 journalmatch = _SYSTEMD_UNIT=sendmail.service
diff --git a/fail2ban/client/fail2banclient.py b/fail2ban/client/fail2banclient.py
index a7053034..917d2498 100755
--- a/fail2ban/client/fail2banclient.py
+++ b/fail2ban/client/fail2banclient.py
@@ -196,7 +196,7 @@ class Fail2banClient(Fail2banCmdLine, Thread):
 				th.daemon = True
 				th.start()
 				# Mark current (main) thread as daemon:
-				self.setDaemon(True)
+				self.daemon = True
 				# Start server direct here in main thread (not fork):
 				self._server = Fail2banServer.startServerDirect(self._conf, False)
 
diff --git a/fail2ban/server/server.py b/fail2ban/server/server.py
index 36ed1b0d..60a60cd7 100644
--- a/fail2ban/server/server.py
+++ b/fail2ban/server/server.py
@@ -849,6 +849,26 @@ class Server:
 	def getDatabase(self):
 		return self.__db
 
+	@staticmethod
+	def __get_fdlist():
+		"""Generate a list of open file descriptors.
+		
+		This wouldn't work on some platforms, or if proc/fdescfs not mounted, or a chroot environment,
+		then it'd raise a FileExistsError.
+		"""
+		for path in (
+			'/proc/self/fd', # Linux, Cygwin and NetBSD
+			'/proc/fd',      # MacOS and FreeBSD
+		):
+			if os.path.exists(path):
+				def fdlist():
+					for name in os.listdir(path):
+						if name.isdigit():
+							yield int(name)
+				return fdlist()
+		# other platform or unmounted, chroot etc:
+		raise FileExistsError("fd-list not found")
+
 	def __createDaemon(self): # pragma: no cover
 		""" Detach a process from the controlling terminal and run it in the
 			background as a daemon.
@@ -906,25 +926,37 @@ class Server:
 			# Signal to exit, parent of the first child.
 			return None
 	
-		# Close all open files.  Try the system configuration variable, SC_OPEN_MAX,
+		# Close all open files. Try to obtain the range of open descriptors directly.
+		# As a fallback try the system configuration variable, SC_OPEN_MAX,
 		# for the maximum number of open files to close.  If it doesn't exist, use
 		# the default value (configurable).
 		try:
-			maxfd = os.sysconf("SC_OPEN_MAX")
-		except (AttributeError, ValueError):
-			maxfd = 256	   # default maximum
+			fdlist = self.__get_fdlist()
+			maxfd = -1
+		except:
+			try:
+				maxfd = os.sysconf("SC_OPEN_MAX")
+			except (AttributeError, ValueError):
+				maxfd = 256	   # default maximum
+			fdlist = xrange(maxfd+1)
 	
 		# urandom should not be closed in Python 3.4.0. Fixed in 3.4.1
 		# http://bugs.python.org/issue21207
 		if sys.version_info[0:3] == (3, 4, 0): # pragma: no cover
 			urandom_fd = os.open("/dev/urandom", os.O_RDONLY)
-			for fd in range(0, maxfd):
+			for fd in fdlist:
 				try:
 					if not os.path.sameopenfile(urandom_fd, fd):
 						os.close(fd)
 				except OSError:   # ERROR (ignore)
 					pass
 			os.close(urandom_fd)
+		elif maxfd == -1:
+			for fd in fdlist:
+				try:
+					os.close(fd)
+				except OSError:   # ERROR (ignore)
+					pass
 		else:
 			os.closerange(0, maxfd)
 	
diff --git a/fail2ban/tests/files/logs/sendmail-auth b/fail2ban/tests/files/logs/sendmail-auth
index f88cde86..c7cc28de 100644
--- a/fail2ban/tests/files/logs/sendmail-auth
+++ b/fail2ban/tests/files/logs/sendmail-auth
@@ -32,3 +32,5 @@ May 24 01:59:07 server sm-mta[65815]: 14NNx65Q065815: AUTH failure (CRAM-MD5): u
 May 29 23:14:04 mail sendmail[5976]: 09DJDgOM005976: AUTH failure (login): authentication failure (-13) SASL(-13): authentication failure: checkpass failed, user=test, relay=host.example.com [192.0.2.7] (may be forged)
 # failJSON: { "time": "2005-05-29T23:14:04", "match": true , "host": "192.0.2.8", "desc": "authentication failure, sendmail 8.16.1 (gh-2757)" }
 May 29 23:14:04 mail sendmail[5976]: 09DJDgOM005976: AUTH failure (PLAIN): authentication failure (-13) SASL(-13): authentication failure: Password verification failed, user=test, relay=host.example.com [192.0.2.8]
+# failJSON: { "time": "2005-05-29T23:14:05", "match": true , "host": "192.0.2.9", "desc": "authentication failure, no user part (gh-2757)" }
+May 29 23:14:05 server sendmail[25411]: 26H8MRrS025411: AUTH failure (LOGIN): authentication failure (-13) SASL(-13): authentication failure: checkpass failed, relay=[192.0.2.9]