diff --git a/django_mailbox/models.py b/django_mailbox/models.py
index 0f0ac9d..bfdda0a 100644
--- a/django_mailbox/models.py
+++ b/django_mailbox/models.py
@@ -17,6 +17,7 @@ import mimetypes
 import os.path
 import sys
 import uuid
+from datetime import timedelta
 from tempfile import NamedTemporaryFile
 
 import django
@@ -35,6 +36,8 @@ from django_mailbox.transports import Pop3Transport, ImapTransport, \
 
 logger = logging.getLogger(__name__)
 
+INITIAL_IMPORT_LOOKBACK_DAYS = 365
+
 
 class MailboxQuerySet(models.QuerySet):
     def get_new_mail(self):
@@ -420,7 +423,12 @@ class Mailbox(models.Model):
         connection = self.get_connection()
         if not connection:
             return
-        for message in connection.get_message(condition):
+
+        since = self.last_polling
+        if since is None:
+            since = now() - timedelta(days=INITIAL_IMPORT_LOOKBACK_DAYS)
+
+        for message in connection.get_message_ro(since=since):
             msg = self.process_incoming_message(message)
             if not msg is None:
                 yield msg
diff --git a/django_mailbox/transports/generic.py b/django_mailbox/transports/generic.py
index 5832fda..a43918a 100644
--- a/django_mailbox/transports/generic.py
+++ b/django_mailbox/transports/generic.py
@@ -24,3 +24,6 @@ class GenericFileMailbox(EmailTransport):
             yield message
         repository.flush()
         repository.unlock()
+
+    def get_message_ro(self, since=None):
+        raise NotImplementedError("GenericFileMailbox.get_message_ro not implemented!")
diff --git a/django_mailbox/transports/imap.py b/django_mailbox/transports/imap.py
index 2599ada..fc6951b 100644
--- a/django_mailbox/transports/imap.py
+++ b/django_mailbox/transports/imap.py
@@ -99,19 +99,47 @@ class ImapTransport(EmailTransport):
         if not message_ids:
             return
 
-        # Limit the uids to the small ones if we care about that
-        if self.max_message_size:
-            message_ids = self._get_small_message_ids(message_ids)
-
         if self.archive:
             typ, folders = self.server.list(pattern=self.archive)
             if folders[0] is None:
                 # If the archive folder does not exist, create it
                 self.server.create(self.archive)
 
+        for message in self._iter_messages(message_ids):
+            yield message
+
+        self.server.expunge()
+        return
+
+    def get_message_ro(self, since):
+        """Read-only version of `get_message`. Uses a timestamp to fetch only messages
+        originating later than `since` parameter.
+        """
+
+        date_format = "%d-%b-%Y"
+        typ, [raw_msg_ids] = self.server.search(None, '(since "%s")' % (since.strftime(date_format)))
+
+        message_ids = raw_msg_ids.decode().split()
+
+        if not message_ids:
+            return
+
+        for message in self._iter_messages(message_ids, archive=False, delete=False):
+            yield message
+
+        self.server.expunge()
+        return
+
+
+    def _iter_messages(self, message_ids, condition=None, archive=True, delete=True):
+
+        # Limit the uids to the small ones if we care about that
+        if self.max_message_size:
+            message_ids = self._get_small_message_ids(message_ids)
+
         for uid in message_ids:
             try:
-                typ, msg_contents = self.server.uid('fetch', uid, '(RFC822)')
+                typ, msg_contents = self.server.fetch(uid, '(RFC822)')
                 if not msg_contents:
                     continue
                 try:
@@ -129,9 +157,8 @@ class ImapTransport(EmailTransport):
             except MessageParseError:
                 continue
 
-            if self.archive:
+            if archive and self.archive:
                 self.server.uid('copy', uid, self.archive)
 
-            self.server.uid('store', uid, "+FLAGS", "(\\Deleted)")
-        self.server.expunge()
-        return
+            if delete:
+                self.server.uid('store', uid, "+FLAGS", "(\\Deleted)")
\ No newline at end of file
diff --git a/django_mailbox/transports/pop3.py b/django_mailbox/transports/pop3.py
index 6dbe995..526538e 100644
--- a/django_mailbox/transports/pop3.py
+++ b/django_mailbox/transports/pop3.py
@@ -42,3 +42,6 @@ class Pop3Transport(EmailTransport):
             self.server.dele(i + 1)
         self.server.quit()
         return
+
+    def get_message_ro(self, since=None):
+        raise NotImplementedError("Pop3Transport.get_message_ro not implemented!")
\ No newline at end of file