diff --git a/imap-proto/src/builders/command.rs b/imap-proto/src/builders/command.rs
index 2f672b0..57b9cd2 100644
--- a/imap-proto/src/builders/command.rs
+++ b/imap-proto/src/builders/command.rs
@@ -255,6 +255,7 @@ fn push_attr(cmd: &mut Vec<u8>, attr: Attribute) {
             Attribute::Uid => "UID",
             Attribute::GmailLabels => "X-GM-LABELS",
             Attribute::GmailMsgId => "X-GM-MSGID",
+            Attribute::GmailThrId => "X-GM-THRID",
         }
         .as_bytes(),
     );
diff --git a/imap-proto/src/parser/gmail.rs b/imap-proto/src/parser/gmail.rs
index 209f660..feb8c1e 100644
--- a/imap-proto/src/parser/gmail.rs
+++ b/imap-proto/src/parser/gmail.rs
@@ -38,6 +38,18 @@ pub(crate) fn mailbox_data_gmail_msgid(i: &[u8]) -> IResult<&[u8], MailboxDatum>
     map(gmail_msgid, MailboxDatum::GmailMsgId)(i)
 }
 
+pub(crate) fn gmail_thrid(i: &[u8]) -> IResult<&[u8], u64> {
+    preceded(tag_no_case("X-GM-THRID "), number_64)(i)
+}
+
+pub(crate) fn msg_att_gmail_thrid(i: &[u8]) -> IResult<&[u8], AttributeValue> {
+    map(gmail_thrid, AttributeValue::GmailThrId)(i)
+}
+
+pub(crate) fn mailbox_data_gmail_thrid(i: &[u8]) -> IResult<&[u8], MailboxDatum> {
+    map(gmail_thrid, MailboxDatum::GmailThrId)(i)
+}
+
 #[cfg(test)]
 mod tests {
     use crate::types::*;
@@ -79,4 +91,22 @@ mod tests {
             }
         }
     }
+
+    #[test]
+    fn test_gmail_thrid() {
+        let env = br#"X-GM-THRID 1278455344230334865 "#;
+        match super::msg_att_gmail_thrid(env) {
+            Ok((_, AttributeValue::GmailThrId(thrid))) => {
+                println!("{thrid:?}");
+                assert_eq!(1278455344230334865, thrid);
+            }
+            rsp => {
+                let e = rsp.unwrap_err();
+                if let nom::Err::Error(i) = &e {
+                    println!("{:?}", std::str::from_utf8(i.input));
+                }
+                panic!("unexpected response {e:?}");
+            }
+        }
+    }
 }
diff --git a/imap-proto/src/parser/rfc3501/mod.rs b/imap-proto/src/parser/rfc3501/mod.rs
index 91d1792..98b66e4 100644
--- a/imap-proto/src/parser/rfc3501/mod.rs
+++ b/imap-proto/src/parser/rfc3501/mod.rs
@@ -378,6 +378,7 @@ fn mailbox_data(i: &[u8]) -> IResult<&[u8], MailboxDatum> {
         mailbox_data_search,
         gmail::mailbox_data_gmail_labels,
         gmail::mailbox_data_gmail_msgid,
+        gmail::mailbox_data_gmail_thrid,
         rfc5256::mailbox_data_sort,
     ))(i)
 }
@@ -574,6 +575,7 @@ fn msg_att(i: &[u8]) -> IResult<&[u8], AttributeValue> {
         msg_att_uid,
         gmail::msg_att_gmail_labels,
         gmail::msg_att_gmail_msgid,
+        gmail::msg_att_gmail_thrid,
     ))(i)
 }
 
diff --git a/imap-proto/src/types.rs b/imap-proto/src/types.rs
index 329675c..5f42175 100644
--- a/imap-proto/src/types.rs
+++ b/imap-proto/src/types.rs
@@ -238,6 +238,7 @@ pub enum MailboxDatum<'a> {
     },
     GmailLabels(Vec<Cow<'a, str>>),
     GmailMsgId(u64),
+    GmailThrId(u64),
 }
 
 impl<'a> MailboxDatum<'a> {
@@ -282,6 +283,7 @@ impl<'a> MailboxDatum<'a> {
                 MailboxDatum::GmailLabels(labels.into_iter().map(to_owned_cow).collect())
             }
             MailboxDatum::GmailMsgId(msgid) => MailboxDatum::GmailMsgId(msgid),
+            MailboxDatum::GmailThrId(thrid) => MailboxDatum::GmailThrId(thrid),
         }
     }
 }
@@ -318,6 +320,7 @@ pub enum Attribute {
     /// https://developers.google.com/gmail/imap/imap-extensions#access_to_gmail_labels_x-gm-labels
     GmailLabels,
     GmailMsgId,
+    GmailThrId,
 }
 
 #[derive(Debug, Eq, PartialEq)]
@@ -355,6 +358,7 @@ pub enum AttributeValue<'a> {
     /// https://developers.google.com/gmail/imap/imap-extensions#access_to_gmail_labels_x-gm-labels
     GmailLabels(Vec<Cow<'a, str>>),
     GmailMsgId(u64),
+    GmailThrId(u64),
 }
 
 impl<'a> AttributeValue<'a> {
@@ -385,6 +389,7 @@ impl<'a> AttributeValue<'a> {
                 AttributeValue::GmailLabels(v.into_iter().map(to_owned_cow).collect())
             }
             AttributeValue::GmailMsgId(v) => AttributeValue::GmailMsgId(v),
+            AttributeValue::GmailThrId(v) => AttributeValue::GmailThrId(v),
         }
     }
 }