diff --git a/bridge/slack/handlers.go b/bridge/slack/handlers.go
index 0335b33e..840deafd 100644
--- a/bridge/slack/handlers.go
+++ b/bridge/slack/handlers.go
@@ -75,7 +75,7 @@ func (b *Bslack) handleSlackClient(messages chan *config.Message) {
 			// When we join a channel we update the full list of users as
 			// well as the information for the channel that we joined as this
 			// should now tell that we are a member of it.
-			b.populateUsers()
+			b.populateUsers(false)
 
 			b.channelsMutex.Lock()
 			b.channelsByID[ev.Channel.ID] = &ev.Channel
@@ -83,13 +83,16 @@ func (b *Bslack) handleSlackClient(messages chan *config.Message) {
 			b.channelsMutex.Unlock()
 		case *slack.ConnectedEvent:
 			b.si = ev.Info
-			b.populateChannels()
-			b.populateUsers()
+			b.populateChannels(true)
+			b.populateUsers(true)
 		case *slack.InvalidAuthEvent:
 			b.Log.Fatalf("Invalid Token %#v", ev)
 		case *slack.ConnectionErrorEvent:
 			b.Log.Errorf("Connection failed %#v %#v", ev.Error(), ev.ErrorObj)
+		case *slack.MemberJoinedChannelEvent:
+			b.populateUser(ev.User)
 		default:
+			b.Log.Debugf("Unhandled incoming event: %T", ev)
 		}
 	}
 }
@@ -197,7 +200,7 @@ func (b *Bslack) handleMessageEvent(ev *slack.MessageEvent) (*config.Message, er
 func (b *Bslack) handleStatusEvent(ev *slack.MessageEvent, rmsg *config.Message) bool {
 	switch ev.SubType {
 	case sChannelJoined, sMemberJoined:
-		b.populateUsers()
+		b.populateUsers(false)
 		// There's no further processing needed on channel events
 		// so we return 'true'.
 		return true
@@ -205,7 +208,7 @@ func (b *Bslack) handleStatusEvent(ev *slack.MessageEvent, rmsg *config.Message)
 		rmsg.Username = sSystemUser
 		rmsg.Event = config.EventJoinLeave
 	case sChannelTopic, sChannelPurpose:
-		b.populateChannels()
+		b.populateChannels(false)
 		rmsg.Event = config.EventTopicChange
 	case sMessageChanged:
 		rmsg.Text = ev.SubMessage.Text
diff --git a/bridge/slack/helpers.go b/bridge/slack/helpers.go
index bbe95320..fb7a25d5 100644
--- a/bridge/slack/helpers.go
+++ b/bridge/slack/helpers.go
@@ -63,15 +63,38 @@ func (b *Bslack) getChannelBy(lookupKey string, lookupMap map[string]*slack.Chan
 
 const minimumRefreshInterval = 10 * time.Second
 
-func (b *Bslack) populateUsers() {
+func (b *Bslack) populateUser(userID string) {
+	b.usersMutex.RLock()
+	_, exists := b.users[userID]
+	b.usersMutex.RUnlock()
+	if exists {
+		// already in cache
+		return
+	}
+
+	user, err := b.sc.GetUserInfo(userID)
+	if err != nil {
+		b.Log.Debugf("GetUserInfo failed for %v: %v", userID, err)
+		return
+	}
+
+	b.usersMutex.Lock()
+	b.users[userID] = user
+	b.usersMutex.Unlock()
+}
+
+func (b *Bslack) populateUsers(wait bool) {
 	b.refreshMutex.Lock()
-	if time.Now().Before(b.earliestUserRefresh) || b.refreshInProgress {
+	if !wait && (time.Now().Before(b.earliestUserRefresh) || b.refreshInProgress) {
 		b.Log.Debugf("Not refreshing user list as it was done less than %v ago.",
 			minimumRefreshInterval)
 		b.refreshMutex.Unlock()
 
 		return
 	}
+	for b.refreshInProgress {
+		time.Sleep(time.Second)
+	}
 	b.refreshInProgress = true
 	b.refreshMutex.Unlock()
 
@@ -107,14 +130,17 @@ func (b *Bslack) populateUsers() {
 	b.refreshInProgress = false
 }
 
-func (b *Bslack) populateChannels() {
+func (b *Bslack) populateChannels(wait bool) {
 	b.refreshMutex.Lock()
-	if time.Now().Before(b.earliestChannelRefresh) || b.refreshInProgress {
+	if !wait && (time.Now().Before(b.earliestChannelRefresh) || b.refreshInProgress) {
 		b.Log.Debugf("Not refreshing channel list as it was done less than %v seconds ago.",
 			minimumRefreshInterval)
 		b.refreshMutex.Unlock()
 		return
 	}
+	for b.refreshInProgress {
+		time.Sleep(time.Second)
+	}
 	b.refreshInProgress = true
 	b.refreshMutex.Unlock()
 
@@ -250,7 +276,7 @@ func (b *Bslack) populateMessageWithBotInfo(ev *slack.MessageEvent, rmsg *config
 	}
 	b.Log.Debugf("Found bot %#v", bot)
 
-	if bot.Name != "" && bot.Name != "Slack API Tester" {
+	if bot.Name != "" {
 		rmsg.Username = bot.Name
 		if ev.Username != "" {
 			rmsg.Username = ev.Username
diff --git a/bridge/slack/slack.go b/bridge/slack/slack.go
index 225e16e9..d8dfc62f 100644
--- a/bridge/slack/slack.go
+++ b/bridge/slack/slack.go
@@ -160,7 +160,7 @@ func (b *Bslack) JoinChannel(channel config.ChannelInfo) error {
 		return nil
 	}
 
-	b.populateChannels()
+	b.populateChannels(false)
 
 	channelInfo, err := b.getChannel(channel.Name)
 	if err != nil {
diff --git a/changelog.md b/changelog.md
index 71f7f3f1..fdd6e980 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,9 @@
+# v1.12.3
+## Bugfix
+* slack: Fix bot (legacy token) messages not being send. Closes #571
+* slack: Populate user on channel join (slack) (#644)
+* slack: Add wait option for populateUsers/Channels (slack) Fixes #579 (#653)
+
 # v1.12.2
 
 ## Bugfix
diff --git a/matterbridge.go b/matterbridge.go
index e713fb0b..894051b0 100644
--- a/matterbridge.go
+++ b/matterbridge.go
@@ -15,7 +15,7 @@ import (
 )
 
 var (
-	version = "1.12.3-dev"
+	version = "1.12.4-dev"
 	githash string
 )