diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index 81ea210cf815a4..746811bd559412 100644
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -830,10 +830,11 @@ def get_message(self, key):
         """Return a Message representation or raise a KeyError."""
         start, stop = self._lookup(key)
         self._file.seek(start)
-        from_line = self._file.readline().replace(linesep, b'')
+        from_line = self._file.readline().replace(linesep, b'').decode('ascii')
         string = self._file.read(stop - self._file.tell())
         msg = self._message_factory(string.replace(linesep, b'\n'))
-        msg.set_from(from_line[5:].decode('ascii'))
+        msg.set_unixfrom(from_line)
+        msg.set_from(from_line[5:])
         return msg
 
     def get_string(self, key, from_=False):
diff --git a/Lib/test/test_mailbox.py b/Lib/test/test_mailbox.py
index d84faad0eb3406..c52c014185bec7 100644
--- a/Lib/test/test_mailbox.py
+++ b/Lib/test/test_mailbox.py
@@ -1127,12 +1127,14 @@ def test_add_from_string(self):
         # Add a string starting with 'From ' to the mailbox
         key = self._box.add('From foo@bar blah\nFrom: foo\n\n0\n')
         self.assertEqual(self._box[key].get_from(), 'foo@bar blah')
+        self.assertEqual(self._box[key].get_unixfrom(), 'From foo@bar blah')
         self.assertEqual(self._box[key].get_payload(), '0\n')
 
     def test_add_from_bytes(self):
         # Add a byte string starting with 'From ' to the mailbox
         key = self._box.add(b'From foo@bar blah\nFrom: foo\n\n0\n')
         self.assertEqual(self._box[key].get_from(), 'foo@bar blah')
+        self.assertEqual(self._box[key].get_unixfrom(), 'From foo@bar blah')
         self.assertEqual(self._box[key].get_payload(), '0\n')
 
     def test_add_mbox_or_mmdf_message(self):
@@ -1667,18 +1669,23 @@ def test_initialize_with_unixfrom(self):
         msg = mailbox.Message(_sample_message)
         msg.set_unixfrom('From foo@bar blah')
         msg = mailbox.mboxMessage(msg)
-        self.assertEqual(msg.get_from(), 'foo@bar blah', msg.get_from())
+        self.assertEqual(msg.get_from(), 'foo@bar blah')
+        self.assertEqual(msg.get_unixfrom(), 'From foo@bar blah')
 
     def test_from(self):
         # Get and set "From " line
         msg = mailbox.mboxMessage(_sample_message)
         self._check_from(msg)
+        self.assertIsNone(msg.get_unixfrom())
         msg.set_from('foo bar')
         self.assertEqual(msg.get_from(), 'foo bar')
+        self.assertIsNone(msg.get_unixfrom())
         msg.set_from('foo@bar', True)
         self._check_from(msg, 'foo@bar')
+        self.assertIsNone(msg.get_unixfrom())
         msg.set_from('blah@temp', time.localtime())
         self._check_from(msg, 'blah@temp')
+        self.assertIsNone(msg.get_unixfrom())
 
     def test_flags(self):
         # Use get_flags(), set_flags(), add_flag(), remove_flag()
@@ -1866,6 +1873,7 @@ def test_maildir_to_mboxmmdf(self):
                 self.assertEqual(msg.get_flags(), result)
                 self.assertEqual(msg.get_from(), 'MAILER-DAEMON %s' %
                              time.asctime(time.gmtime(0.0)))
+                self.assertIsNone(msg.get_unixfrom())
             msg_maildir.set_subdir('cur')
             self.assertEqual(class_(msg_maildir).get_flags(), 'RODFA')
 
@@ -1914,10 +1922,12 @@ def test_mboxmmdf_to_mboxmmdf(self):
             msg_mboxMMDF = class_(_sample_message)
             msg_mboxMMDF.set_flags('RODFA')
             msg_mboxMMDF.set_from('foo@bar')
+            self.assertIsNone(msg_mboxMMDF.get_unixfrom())
             for class2_ in (mailbox.mboxMessage, mailbox.MMDFMessage):
                 msg2 = class2_(msg_mboxMMDF)
                 self.assertEqual(msg2.get_flags(), 'RODFA')
                 self.assertEqual(msg2.get_from(), 'foo@bar')
+                self.assertIsNone(msg2.get_unixfrom())
 
     def test_mboxmmdf_to_mh(self):
         # Convert mboxMessage and MMDFMessage to MHMessage
diff --git a/Misc/NEWS.d/next/Library/2023-07-23-12-28-26.gh-issue-75705.aB2-Ww.rst b/Misc/NEWS.d/next/Library/2023-07-23-12-28-26.gh-issue-75705.aB2-Ww.rst
new file mode 100644
index 00000000000000..272e31d64cfbd9
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-07-23-12-28-26.gh-issue-75705.aB2-Ww.rst
@@ -0,0 +1 @@
+Set unixfrom envelope in :class:`mailbox.mbox` and :class:`mailbox.MMDF`.