diff --git a/Changelog.md b/Changelog.md
index ae1d6b76..abd9f5c1 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -36,7 +36,7 @@ Changelog [format](http://keepachangelog.com/en/1.0.0/)
   * Alternative Routing is enabled/disabled by `ClientManager`
   * Logging out of `Clients` is handled/retried asynchronously by `ClientManager`
 * GODT-265 Alternative Routing v2 (more resiliant to short term connection drops)
-
+* GODT-310 Alternative parsing of `References` header (old parsing probably malformed message IDs)
 
 ### Fixed
 * Use correct binary name when finding location of addcert.scpt
diff --git a/internal/imap/mailbox_message.go b/internal/imap/mailbox_message.go
index e1d0e19c..1f907d47 100644
--- a/internal/imap/mailbox_message.go
+++ b/internal/imap/mailbox_message.go
@@ -148,10 +148,10 @@ func (im *imapMailbox) CreateMessage(flags []string, date time.Time, body imap.L
 	if len(referenceList) > 0 {
 		lastReference := referenceList[len(referenceList)-1]
 		// In case we are using a mail client which corrupts headers, try "References" too.
-		re := regexp.MustCompile(`(?U)<.*@protonmail.internalid>`)
-		match := re.FindString(lastReference)
-		if match != "" {
-			internalID = match[1 : len(match)-len("@protonmail.internalid>")]
+		re := regexp.MustCompile(pmapi.InternalReferenceFormat)
+		match := re.FindStringSubmatch(lastReference)
+		if len(match) > 0 {
+			internalID = match[1]
 		}
 	}
 
diff --git a/internal/smtp/user.go b/internal/smtp/user.go
index b2064cd8..5381e8bc 100644
--- a/internal/smtp/user.go
+++ b/internal/smtp/user.go
@@ -370,12 +370,12 @@ func (su *smtpUser) handleReferencesHeader(m *pmapi.Message) (draftID, parentID
 	references := m.Header.Get("References")
 	newReferences := []string{}
 	for _, reference := range strings.Fields(references) {
-		if !strings.Contains(reference, "@protonmail.internalid") {
+		if !strings.Contains(reference, "@"+pmapi.InternalIDDomain) {
 			newReferences = append(newReferences, reference)
 		} else { // internalid is the parentID.
-			idMatch := regexp.MustCompile(`(?U)<.*@protonmail.internalid>`).FindString(reference)
-			if idMatch != "" {
-				lastID := idMatch[1 : len(idMatch)-len("@protonmail.internalid>")]
+			idMatch := regexp.MustCompile(pmapi.InternalReferenceFormat).FindStringSubmatch(reference)
+			if len(idMatch) > 0 {
+				lastID := idMatch[1]
 				filter := &pmapi.MessagesFilter{ID: []string{lastID}}
 				if su.addressID != "" {
 					filter.AddressID = su.addressID
diff --git a/pkg/message/header.go b/pkg/message/header.go
index 388065e1..f2b780f0 100644
--- a/pkg/message/header.go
+++ b/pkg/message/header.go
@@ -74,19 +74,19 @@ func GetHeader(msg *pmapi.Message) textproto.MIMEHeader { //nolint[funlen]
 	}
 	if msg.ID != "" {
 		if h.Get("Message-Id") == "" {
-			h.Set("Message-Id", "<"+msg.ID+"@protonmail.internalid>")
+			h.Set("Message-Id", "<"+msg.ID+"@"+pmapi.InternalIDDomain+">")
 		}
 		h.Set("X-Pm-Internal-Id", msg.ID)
 		// Forward References, and include the message ID here (to improve outlook support).
 		if references := h.Get("References"); !strings.Contains(references, msg.ID) {
-			references += " <" + msg.ID + "@protonmail.internalid>"
+			references += " <" + msg.ID + "@" + pmapi.InternalIDDomain + ">"
 			h.Set("References", references)
 		}
 	}
 	if msg.ConversationID != "" {
 		h.Set("X-Pm-ConversationID-Id", msg.ConversationID)
 		if references := h.Get("References"); !strings.Contains(references, msg.ConversationID) {
-			references += " <" + msg.ConversationID + "@protonmail.conversationid>"
+			references += " <" + msg.ConversationID + "@" + pmapi.ConversationIDDomain + ">"
 			h.Set("References", references)
 		}
 	}
diff --git a/pkg/pmapi/messages.go b/pkg/pmapi/messages.go
index 696fb443..f2c8ddd4 100644
--- a/pkg/pmapi/messages.go
+++ b/pkg/pmapi/messages.go
@@ -141,6 +141,15 @@ const (
 // Due to API limitations, we shouldn't make requests with more than 100 message IDs at a time.
 const messageIDPageSize = 100
 
+// ConversationIDDomain is used as a placeholder for conversation reference headers to improve compatibility with various clients
+const ConversationIDDomain = `protonmail.conversationid`
+
+// InternalIDDomain is used as a placeholder for reference/message ID headers to improve compatibility with various clients
+const InternalIDDomain = `protonmail.internalid`
+
+// InternalReferenceFormat describes format of the message ID (as regex) used for parsing reference headers
+const InternalReferenceFormat = `(?U)<.*@` + InternalIDDomain + `>`
+
 // Message structure.
 type Message struct {
 	ID             string `json:",omitempty"`