clear up some limitations
diff --git a/README.md b/README.md
index 7668d5e..cfd140f 100644
--- a/README.md
+++ b/README.md
@@ -47,16 +47,17 @@
been dropped in favor of collision-secure generators._
### Known Limitations:
-* Not currently suitable as a list archive, as not all emails received for a list are stored.
* If an email is re-imported or archived, entries are currently replaced.
This can result in loss of attributes such as alternate Permalinks and deleted status.
-* The migration tool drops Permalinks if two existing entries point to a sufficiently similar email
-* The migration tool does not fix up badly-parsed message-ids etc
-* There is no longer a 1-to-1 relationship between mbox and source entries.
- This can result in orphan source entries, with implications for privacy redaction.
* emails are filed according to the Date: header, rather than arrival time.
This can cause emails to appear in the wrong month or year, or even be future-dated.
* Whilst the underlying database can handle any number of emails in a month,
- the UI and much of the API cannot, and are not scalable.
+ the UI and much of the API does not scale well beyond around 10,000 emails per month per list.
+
+#### Known limitations when migrating from older Pony Mail instances:
+* The migration tool can drop Permalinks if two existing entries point to a sufficiently similar email
+* The migration tool does not fix up badly-parsed message-ids etc
+* There is no longer a 1-to-1 relationship between mbox and source entries.
+ This can result in orphan source entries, with implications for privacy redaction.
* Header parsing is stricter than before; in particular some unusual Message-IDs are not handled correctly.
This affects use of Foal as a replacement for Apache mod_mbox mail archives.
