diff --git a/TODO b/TODO
index a04b253..43f0c0d 100644
--- a/TODO
+++ b/TODO
@@ -1,7 +1,5 @@
 f{,data}sync() usage could be optimized by batching the calls.
 
-make SSL (connect) timeouts produce a bit more than "Unidentified socket error".
-
 automatically resume upon transient errors, e.g. "connection reset by peer"
 or timeout after some data was already transmitted.
 possibly also try to handle Exchange's "glitches" somehow.
@@ -10,11 +8,16 @@ uidvalidity lock timeout handling would be a good idea.
 
 should complain when multiple Channels match the same folders.
 
+should complain about nonsensical combinations like Sync Pull + Create Both.
+
 propagate folder deletions even when the folders are non-empty.
 - verify that "most" of the folders in the Channel are still there.
 - refuse to delete unpropagated messages when trashing on the remote side.
 - refuse to delete far side if it has unpropagated messages. symmetry?
 
+add option to suppress complaints about folders that would need creation
+(but not deleted ones).
+
 add message expiration based on arrival date (message date would be too
 unreliable). MaxAge; probably mutually exclusive to MaxMessages.
 
@@ -27,11 +30,12 @@ add support for event notification callbacks.
 make it possible to have different mailbox names for far and near side in
 Patterns.
 - use far:near for the pattern
-  - for quoting, use more colons: the longest sequence of colons is the
-    separator
+  - supporting names with colons requires and extension of the parser to
+    report which parts of an argument were quoted
 - this makes Groups mostly useless, as they are mostly a workaround for this
   function being missing so far
 - this is needed for move detection, which would work only within one Channel
+- this supersedes MapInbox
 
 add regexp-based mailbox path rewriting to the drivers. user would provide
 expressions for both directions. every transformation would be immediately
@@ -44,18 +48,22 @@ also: idling mode.
 parallel fetching of multiple mailboxes.
 TLS session resumption becomes interesting then as well.
 
-imap_set_flags(): group commands for efficiency, don't call back until
-imap_commit().
+imap_set_msg_flags() & imap_trash_msg(): group commands for efficiency.
 
 add streaming from fetching to storing.
+this is complicated by the IMAP target needing the final size in advance,
+which we can't know in a single pass when newline translation is necessary.
 
 handle custom flags (keywords).
+this is impeded by there being no Maildir-side standard.
 
 make use of IMAP CONDSTORE extension (rfc4551; CHANGEDSINCE FETCH Modifier);
 make use of IMAP QRESYNC extension (rfc5162) to avoid SEARCH to find vanished
 messages.
 
-use MULTIAPPEND and FETCH with multiple messages.
+make use of IMAP CAPABILITY APPENDLIMIT= extension (rfc7889; fastmail & gmail).
+this is really useful only for IMAP <=> IMAP syncs: saves FETCH BODY.
+the message could still become oversized due to conversion.
 
 dummy messages resulting from MaxSize should contain a dump of the original
 message's MIME structure and its (reasonably sized) text parts.