- bugs

- maildir: if mail file isn't found, it may be because it was renamed

(flag changed). we must then sync the directory and see again if the mail

is found

- we may override mbox dotlock file, but then get stuck at fcntl/flock.

we should check for those before overriding the mbox lock..

- mail-lockdir.c isn't 100% safe.. stale locks are detected by checking

that hard link count is 1, then it's unlink()ed. but what if another

process did the same unlink() + creat() in the middle of our

stat()..unlink()? no easy way to fix this really, just replace it with a

fcntl() lock.

- SEARCH FROM/TO/CC/BCC now generates the field from ENVELOPE which it

uses for matching. This however gives different results than when

matching from headers.

- Outlook Express sometimes says "message not found" when trying to open

one, why?

- reliability fixes:

- if we deleted mail from index but didn't write modify log, other

dovecots don't handle it properly. they either assert at index-sync.c:42

or if new mails have also been added since, they don't notice it at all

actually, that breaks reads as well since we get expunges only from

the old file.. and check that deleting file does "inconsistency error"

- if imap process notices that both modify logs are getting full because

it's client isn't syncing, the client should be disconnected

- what happens if .customflags can't be locked while opening index?

- checks:

- if we have entries in modifylog with UID 10..11, 9..12, 8..13 etc.

do they work correctly?

- check that search message-id worked properly always

- check that search's OR and () work properly

- Should SEARCH SENT* apply timezone?

- make sure SELECT rebuilds index properly when next_uid is near 32bit value

- make sure connection limits work

- enhancements:

- optionally don't fail if index is locked, but build it in memory

- when fetching body/envelope/etc we could try to cache it immediately if

we can get lock with try_lock.

- optionally use only in-memory indexes

- maildir could support also the dirty-flag in messages. files would be

renamed "whenever there's time" (that'd require the indexer program, or

forking and doing it in background)

- optionally keep the message file name as it's UID. Then we don't have to

save the filename anywhere.

- send EXISTS immediately after new mail arrives.

- linux: we can use dnotify for maildir (but not mbox I think, we'd

get interrupted all the time if we checked eg. large /var/spool/mail)

- *bsd: kqueue() can notify changes in mbox and maildir

- .subscriptions currently uses fcntl() locking - maybe we should instead

just write to temp file and rename()? optionally at least, so it

works with NFS.

- OpenSSL: support generated DH parameters

- lib-charset:

- utf8_toupper() is a must. and a bit difficult if we want to do it right.

- add support for other things than iconv() as well? we could reuse

the code from cyrus or courier

- allow index files to be in completely separate location than mail data.

mails could be read through slow NFS access but indexes from fast local

disk. with this thinking it makes more sense to create larger index files

to save for example mail headers. also index rebuilding should be very

light operation, the indexes would be filled while the data is being

accessed by the imap client. of course all this should be optional so

we don't slow down when mails and indexes are stored in same disk.

- we need permanent storage for UIDs. with mbox use X-UID like UW-IMAP,

with maildir a) file:2,flags,Uuid b) file,U=uid:2,flags. uid validity

would be in .uidvalidity file. the b-case would require that to be done

by the client moving it from new/ to cur/

index:

- mbox:

- if a file isn't valid mbox and it's tried to be opened, say it in one

line in error log, not 6..

- empty lines at beginning of file still aren't ignored

- UW-IMAPd writes empty spaces after X-Keywords which it uses so that

it doesn't have to rewrite the whole file if status flags changed

in the beginning of it. We could do that too.

- When expunging the first message we could move the X-IMAPbase header

to next message to avoid full rewriting later.

- UW-IMAP doesn't send it's fields to client: X-IMAPbase, Status,

X-Status, X-Keywords, X-UID.. should we? probably just makes things

more difficult

- COPY 1 copies X-IMAPbase header too which isn't good idea. save() could

actually strip this (and X-UID) while also fixing From-lines etc.

- we need either From-line escaping or writing Content-Length when saving

mails.

- read-only support for mailboxes where we don't have write-access

- we should try to avoid completely rebuilding indexes unless they're

corrupted. especially if we later want to support some read-only boxes

and keep the mail flags only in index file. fsck() could verify that

records are ok, and that if data file isn't ok the record is deleted.

- if .customflags is removed and Maildir files have custom flags, add

"unknown1" "unknown2" etc. flags to .customflags file for each found flag

- when index is being rebuilt, it always complains about tree/modifylog

having wrong indexid..

- log transferred amount of bytes. just a bit problematic who logs it, since

imap-login does SSL transfers but not unencrypted.. could also log SSL

settings (especially compression).

- if we wanted to support huge mailboxes with small memory usage, it'd now

be possible if we just instead of mmap()ing the whole index files would

have maybe 3-4 256k mmap()ed areas which we move based on the need.

- should work fine with .imap.index and .imap.index.data

- log files aren't affected by mailbox size

- if the tree file also kept constantly moving the nodes so that

tree's root was at the beginning of the file, we could use this mmap

caching with it too

- but, is it worth the trouble really? the OS can do all this itself,

only thing we're doing is keeping the processes virtual memory usage

small.

lib-storage:

- support multiple mailbox formats and locations for one user. that would

require support for multiple MailStorages, and since we're chroot()ed,

usually the only way to communicate with others would be to create

RemoteMailStorage which would use TCP/UNIX sockets to connect to another

imap session.

- SEARCH:

- message_body_search() could accept multiple search keywords so we

wouldn't need to call it separately for each one (so we wouldn't need

to parse the message multiple times).

- message_body_search() could support NULL MessagePart and the searching

could be done while parsing the message. this would need changes to

message_parse() as well.

- could optionally support scanning inside file attachments and use

plugins to extract text out of them (word, excel, pdf, etc. etc.)

- use a trie index for fast text searching, like cyrus squat?

- Create our own extension: When searching with TEXT/BODY, return

the message text surrounding the keywords just like web search engines

do. like: SEARCH X-PRINT-MATCHES TEXT "hello" -> * SEARCH 1 "He said:

Hello world!" 2 "Hello, I'm ...". This would be especially useful with

the above attachment scanning.

- DELETE/RENAME: when someone else had the mailbox open, we should

disconnect it (when stat() fails with ENOENT while syncing)

- RENAME INBOX isn't atomic with Maildir. And in general, RENAME can't

move mails between different storages. Maybe support doing also using

COPY + delete once COPY is atomic?

- maildir: atomic COPY could be done by having transaction directories.

Make a "tra" directory at the same level as cur/new/tmp, and make it

have subdirectories in the same way as tmp has temp files. Directory

begins with a "." as long as transaction isn't finished, rename()ing

it away finishes it. All mails under finished dirs must be moved into

new/ directory and the directory removed by any process who notices them.

- we should probably do some light checking that appended mails actually

look like valid rfc822 mails..

- maybe limit the length of custom flags? we don't really have a problem

with them, but with mbox a long X-IMAPbase could break something.. Maybe

configurable, default to 50 chars?

- we could send flag changes after all commands by making expunge/flags sync

counters separate for modify log. flags would need to update the seq

though, too slow?

- things calling message_send() could verify that it wrote enough data.

if not, fill the rest with spaces and return failure. -1 = error,

0 = filled, 1 = ok.

general:

- sieve (rfc3028)

- rfc2231 continuation support

- ulimit / setrlimit() should be set somewhere for imap process. and maybe

also separate limits for data stack and mem pools

- create indexer binary

- imap-login leaks I/O descriptors when killed, that's because the SSL

fds are destroyed lazily.. should we bother fixing..?

- logins are always sent now using syslog(), we'd need to have i_info()

or something so they could also be written to log files.. also make it

possible to log into different log than errors.

- should we bother checking if there's invalid 8bit headers in

BODY/BODYSTRUCTURE output and converting them to quoted printable? well,

several of them are now but not all..

- update docs/index.txt

- support Maildir++ quota

- maybe give more untagged NO/ALERT replies? like when mailbox is in

inconsistent state. and when UIDs are reordered because they're too large.

- *_strdup_printf() functions could use C99 compatible vsnprintf() instead of

printf_string_upper_bound().

- imap/ and lib-imap/ should allow infinite number of custom flags, it's

storage's problem if it can't handle too many of them.

auth / login:

- kchuid, SRP, anonymous SASL

- PAM: support some options so /etc/passwd-lookup isn't needed. uid=x, gid=y,

mailroot=/var/mail. maildirs should be then created when needed

- Digest-MD5: support integrity protection, and maybe crypting. Do it

through imap-login like SSL is done?

- imap-auth should limit how fast authentication requests are allowed from

login processes. especially if there's one login/connection the speed

should be something like once/sec. also limit how fast to accept new

connections.

cleanups / checks:

- grep for FIXME

- check if t_push()/t_pop() should be added somewhere

- allocating readwrite pools now just uses system_pool .. so pool_unref()

can't free memory used by it .. what to do about it? at least count the

malloc/free calls and complain if at the exit they don't match

- ..wonder what it would look like if I did s/FooBarBaz/struct foo_bar_baz/..

- create env_put() and env_clean()

- nearest_power() could be problematic with things that want it for ints,

not size_t..

optional optimizations:

- provide some helper binary to save new mail into mailboxes with CR+LF

line breaks?

- disk I/O is the biggest problem, so split the mail into multiple computers

based on user and have a proxy in the front redirecting the connection.

cyrus had something like this except a lot more complicated - it tried

to fix the problem of having shared mailboxes. we have the same problem

with local shared mailboxes as we don't use same UID for everyone's mail

and we may be chrooted, so locally we could communicate with UNIX sockets,

remotely that could be done with TCP sockets.

capabilities:

- preferrably all should be possible to #ifdef away by a configure

option (--without-capabilities=acl,namespace,...)

- possibility to disable them from config file

- acl (rfc2086, draft-ietf-imapext-acl), namespace (rfc2342)

- probably do it like cyrus. "user.<username>" to access other

users, with "" defaulting to "user.<myself>". these should be

configurable however.

- shared namespaces? maybe configurable in config file

- easiest way to do ACL would be to use unix modes, but is that

useful at all? Well, ACL2 has a bit better support for that, so

maybe we could support it.

- otherwise gets a bit trickly, we could keep all mail in "imapmail"

group and 0600/0700 mode by default, but when mail is shared to others,

the group read/write access bits would be set. or alternatively we

could launch another imap process to handle it, which we should support

anyway. ACLs could be stored into ".acl" ascii file in each folder.

- support for private and shared flags, configurable by mailbox admin.

this isn't in any draft yet, but ACL2 author was going to create one.

[SHAREDFLAGS (...)] would specify which ones are shared, don't know yet

how they would be configured.

- quota (rfc2087, draft-cridland-imap-quota)

- give filesystem values only to admins

- support for Maildir++, probably no need to support more.

quota capability supports complex quota configuration, but if

no mailer supports them we probably shouldn't bother either

- id (rfc2971)

- must be configurable what gets sent, default to only name=Dovecot

- separate pre/post-login settings

- optionally log configured parts of the client information, but only

once, probably at the same time as logging "Logged in",

"Disconnected", etc.

- remember to force truncating values longer than 30 chars,

especially before logging

- mailbox-referrals (rfc2193)

- this is useful whenever we would otherwise need to make the

connection ourself. for example load balancing and shared mailboxes

requiring another UID to run.

- this rfc defines no exact way for server to detect if client

supports referrals or not. I don't think there's much point in

supporting only referrals, as most clients don't support them.

Instead we should return referrals when we know that client

supports them, otherwise do the connecting ourself. If client

issues RLIST or RLSUB command, it's safe to assume it supports

referrals.

- for load balancing this works just fine, but what about shared

mailboxes which require different UID? If we login with our own

username, we end up with our own UID instead of what we wanted.

IMAP URLs don't support separated authorization id which would

have made this very easy.. We could give the "userid@group" as

userid, but clients probably treat it as different userid and

ask the password again.

- problems, problems, .. maybe not worth the trouble.

- literal+ (rfc2088)

- simple. in case of invalid data, just disconnect client.

- idle (rfc2177)

- just call the syncing every few seconds (configurable)

- with Linux we can use fcntl() and F_SETSIG to provide fast checks.

just make sure sync() still won't be called more than once in a

few seconds

- uidplus (rfc2359)

- uid expunge: no problem

- append, copy: oh no. these would slow down things and make

handling them much more difficult. currently we just store the

mails to destination mailbox without touching the indexes. since

we'd need to know their final UID, we'd have to lock the indexes

and mbox) fsck() first and append() next to find out the uid,

maildir) move the mail directly into cur/ and index it.

- unselect (no draft or anything AFAIK)

- like CLOSE, but doesn't expunge mails. easy.

- drafts:

- http://www.imc.org/ids.html

- multiappend (draft-crispin-imap-multiappend)

- shouldn't have any problems

- listext (draft-ietf-imapext-list-extensions)

- well, it expired January 2002.. I like it though.

- children (draft-gahrns-imap-child-mailbox)

- I like listext more.. They have the same functionality though,

so pretty easy to support both if needed

- annotate (draft-ietf-imapext-annotate)

- per-message annotations. this will be major change. especially

because currently there's no suitable storage for them, and

they'll probably change all the time.. maybe if we moved into

berkeley db to store the .data file and these annotations.

- annotatemore (draft-daboo-imap-annotatemore)

- server and per-mailbox annotations. much easier than

per-message annotations, but they'd be easier to place into

db as well.

- binary (draft-nerenberg-imap-binary)

- perhaps not too useful. I'd like to make Dovecot fully

binary-safe though.

- sort (draft-ietf-imapext-sort)

- basically sorted SEARCH, requiring CHARSET support for

UTF-8 and ASCII

- we could create alternative binary tree file(s) for different sort

conditions, ".tree-sort" or something. or if we decide to just

keep it in memory, btree could still be best choice.

- required by squirrelmail (webmail)

- thread (draft-ietf-imapext-thread)

- basically SORT but reply with thread lists

- possibly use a binary tree too .. or maybe it's enough to use the

sort-tree and then just pick up the references separately? have to

check more carefully later.

- view (draft-ietf-imapext-view)

- slow, complex, luckily draft expired almost two years ago.

i hope i don't have to implement this :)

- can be done client-side just fine (evolution's virtual folders)