diff --git a/http2irc.py b/http2irc.py
index 14822eb..5a98c25 100644
--- a/http2irc.py
+++ b/http2irc.py
@@ -288,6 +288,7 @@ class IRCClientProtocol(asyncio.Protocol):
 		self.pongReceivedEvent = asyncio.Event()
 		self.sasl = bool(self.config['irc']['certfile'] and self.config['irc']['certkeyfile'])
 		self.authenticated = False
+		self.usermask = None
 
 	@staticmethod
 	def nick_command(nick: str):
@@ -298,6 +299,11 @@ class IRCClientProtocol(asyncio.Protocol):
 		nickb = nick.encode('utf-8')
 		return b'USER ' + nickb + b' ' + nickb + b' ' + nickb + b' :' + real.encode('utf-8')
 
+	def _maybe_set_usermask(self, usermask):
+		if b'@' in usermask and b'!' in usermask.split(b'@')[0] and all(x not in usermask for x in (b' ', b'*', b'#', b'&')):
+			self.usermask = usermask
+			self.logger.debug(f'Usermask is now {usermask!r}')
+
 	def connection_made(self, transport):
 		self.logger.info('IRC connected')
 		self.transport = transport
@@ -386,11 +392,12 @@ class IRCClientProtocol(asyncio.Protocol):
 				break
 			channelB = channel.encode('utf-8')
 			messageB = message.encode('utf-8')
-			if len(b'PRIVMSG ' + channelB + b' :' + messageB) > 510:
+			usermaskPrefixLength = 1 + (len(self.usermask) if self.usermask else 100) + 1
+			if usermaskPrefixLength + len(b'PRIVMSG ' + channelB + b' :' + messageB) > 510:
 				self.logger.debug(f'Splitting up into smaller messages')
 				# Message too long, need to split. First try to split on spaces, then on codepoints. Ideally, would use graphemes between, but that's too complicated.
 				prefix = b'PRIVMSG ' + channelB + b' :'
-				prefixLength = len(prefix)
+				prefixLength = usermaskPrefixLength + len(prefix) # Need to account for the origin prefix included by the ircd when sending to others
 				maxMessageLength = 510 - prefixLength # maximum length of the message part within each line
 				messages = []
 				while message:
@@ -463,7 +470,8 @@ class IRCClientProtocol(asyncio.Protocol):
 
 	def message_received(self, message):
 		self.logger.debug(f'Message received: {message!r}')
-		if message.startswith(b':'):
+		rawMessage = message
+		if message.startswith(b':') and b' ' in message:
 			# Prefixed message, extract command + parameters (the prefix cannot contain a space)
 			message = message.split(b' ', 1)[1]
 
@@ -482,6 +490,13 @@ class IRCClientProtocol(asyncio.Protocol):
 				self.transport.close()
 		elif message == b'AUTHENTICATE +':
 			self.send(b'AUTHENTICATE +')
+		elif message.startswith(b'900 '): # "You are now logged in", includes the usermask
+			words = message.split(b' ')
+			if len(words) >= 3 and b'!' in words[2] and b'@' in words[2]:
+				if b'!~' not in words[2]:
+					# At least Charybdis seems to always return the user without a tilde, even if identd failed. Assume no identd and account for that extra tilde.
+					words[2] = words[2].replace(b'!', b'!~', 1)
+				self._maybe_set_usermask(words[2])
 		elif message.startswith(b'903 '): # SASL auth successful
 			self.authenticated = True
 			self.send(b'CAP END')
@@ -527,6 +542,28 @@ class IRCClientProtocol(asyncio.Protocol):
 			asyncio.create_task(self.send_messages())
 			asyncio.create_task(self.confirm_messages())
 
+		# JOIN success
+		elif message.startswith(b'JOIN ') and not self.usermask:
+			# If this is my own join message, it should contain the usermask in the prefix
+			if rawMessage.startswith(b':' + self.config['irc']['nick'].encode('utf-8') + b'!') and b' ' in rawMessage:
+				usermask = rawMessage.split(b' ', 1)[0][1:]
+				self._maybe_set_usermask(usermask)
+
+		# Services host change
+		elif message.startswith(b'396 '):
+			words = message.split(b' ')
+			if len(words) >= 3:
+				# Sanity check inspired by irssi src/irc/core/irc-servers.c
+				if not any(x in words[2] for x in (b'*', b'?', b'!', b'#', b'&', b' ')) and not any(words[2].startswith(x) for x in (b'@', b':', b'-')) and words[2][-1:] != b'-':
+					if b'@' in words[2]: # user@host
+						self._maybe_set_usermask(self.config['irc']['nick'].encode('utf-8') + b'!' + words[2])
+					else: # host (get user from previous mask or settings)
+						if self.usermask:
+							user = self.usermask.split(b'@')[0].split(b'!')[1]
+						else:
+							user = b'~' + self.config['irc']['nick'].encode('utf-8')
+						self._maybe_set_usermask(self.config['irc']['nick'].encode('utf-8') + b'!' + user + b'@' + words[2])
+
 	def connection_lost(self, exc):
 		self.logger.info('IRC connection lost')
 		self.connected = False