diff --git a/lib/net/imap/response_parser.rb b/lib/net/imap/response_parser.rb
index 189bc980..2c1d1dd1 100644
--- a/lib/net/imap/response_parser.rb
+++ b/lib/net/imap/response_parser.rb
@@ -1888,12 +1888,17 @@ def text?
       # We leniently re-interpret this as
       #   resp-text       = ["[" resp-text-code "]" [SP [text]] / [text]
       def resp_text
+        state = current_state
         if lbra?
           code = resp_text_code; rbra
           ResponseText.new(code, SP? && text? || "")
         else
           ResponseText.new(nil, text? || "")
         end
+      rescue ResponseParseError => error
+        raise if /\buid-set\b/i.match? error.message
+        restore_state state
+        text
       end
 
       # RFC3501 (See https://www.rfc-editor.org/errata/rfc3501):
diff --git a/lib/net/imap/response_parser/parser_utils.rb b/lib/net/imap/response_parser/parser_utils.rb
index 880d4cc2..99626d03 100644
--- a/lib/net/imap/response_parser/parser_utils.rb
+++ b/lib/net/imap/response_parser/parser_utils.rb
@@ -221,8 +221,14 @@ def exception(message) = ResponseParseError.new(
           message, parser_state:, parser_class: self.class
         )
 
-        def current_state = [@lex_state, @pos, @token]
-        def parser_state  = [@str, *current_state]
+        # This can be used to backtrack after a parse error, and re-attempt to
+        # parse using a fallback.
+        #
+        # NOTE: Reckless backtracking could lead to O(n²) situations, so this
+        # should very rarely be used.  Ideally, fallbacks should not backtrack.
+        def restore_state(state) = (@lex_state, @pos, @token = state)
+        def current_state        = [@lex_state, @pos, @token]
+        def parser_state         = [@str, *current_state]
 
       end
     end
diff --git a/test/net/imap/fixtures/response_parser/quirky_behaviors.yml b/test/net/imap/fixtures/response_parser/quirky_behaviors.yml
index e6bf9d48..f6f3e790 100644
--- a/test/net/imap/fixtures/response_parser/quirky_behaviors.yml
+++ b/test/net/imap/fixtures/response_parser/quirky_behaviors.yml
@@ -31,6 +31,33 @@
         unparsed_data: "froopy snood"
       raw_data: "* 86 NOOP froopy snood\r\n"
 
+  "Microsoft Exchange issues an invalid resp-text-code":
+    comment: |
+      net-imap issue: https://github.com/ruby/net-imap/issues/597
+
+      Microsoft Exchange is issuing an invalid resp-text-code, but net-imap
+      should fallback to `resp-text = text` when resp-text-code fails to parse.
+    :debug: false # current version of backtracking still prints parse_errors
+    :response: "RUBY0001 OK [Error=\"Microsoft.Exchange.Data.Storage.WrongServerException:
+      Cross Server access is not allowed for mailbox xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx\"
+      AuthResultFromPopImapEnd=0 Proxy=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM:1993:SSL
+      MailboxBE=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM
+      Service=Imap4] AUTHENTICATE completed.\r\n"
+    :expected: !ruby/struct:Net::IMAP::TaggedResponse
+      tag:  RUBY0001
+      name: OK
+      data: '[Error="Microsoft.Exchange.Data.Storage.WrongServerException: Cross Server
+        access is not allowed for mailbox xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+        AuthResultFromPopImapEnd=0
+        Proxy=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM:1993:SSL
+        MailboxBE=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM Service=Imap4]
+        AUTHENTICATE completed.'
+      raw_data: "RUBY0001 OK [Error=\"Microsoft.Exchange.Data.Storage.WrongServerException:
+        Cross Server access is not allowed for mailbox xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx\"
+        AuthResultFromPopImapEnd=0 Proxy=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM:1993:SSL
+        MailboxBE=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM Service=Imap4] AUTHENTICATE
+        completed.\r\n"
+
   outlook.com puts an extra SP in ENVELOPE address lists:
     comment: |
       An annoying bug from outlook.com.  They've had the bug for years, and