diff --git a/Lib/imaplib.py b/Lib/imaplib.py
index 10ff340ef96..826eea25248 100644
--- a/Lib/imaplib.py
+++ b/Lib/imaplib.py
@@ -37,11 +37,12 @@ AllowedVersions = ('IMAP4REV1', 'IMAP4')        # Most recent first
 
 # Maximal line length when calling readline(). This is to prevent
 # reading arbitrary length lines. RFC 3501 and 2060 (IMAP 4rev1)
-# don't specify a line length. RFC 2683 however suggests limiting client
-# command lines to 1000 octets and server command lines to 8000 octets.
-# We have selected 10000 for some extra margin and since that is supposedly
-# also what UW and Panda IMAP does.
-_MAXLINE = 10000
+# don't specify a line length. RFC 2683 suggests limiting client
+# command lines to 1000 octets and that servers should be prepared
+# to accept command lines up to 8000 octets, so we used to use 10K here.
+# In the modern world (eg: gmail) the response to, for example, a
+# search command can be quite large, so we now use 1M.
+_MAXLINE = 1000000
 
 
 #       Commands
diff --git a/Misc/NEWS b/Misc/NEWS
index 111a2801cbf..761f2fb07f2 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -21,6 +21,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #23647: Increase impalib's MAXLINE to accommodate modern mailbox sizes.
+
 - Issue #23539: If body is None, http.client.HTTPConnection.request now sets
   Content-Length to 0 for PUT, POST, and PATCH headers to avoid 411 errors from
   some web servers.