This is a very old list that hasn't been updated for some time. Some items may no longer make sense.
- Convert os.c into a directory of separate functions, with the macro switches defined elsewhere. Then make it into a library.
- Use a pointer to an address structure for expanding $domain etc, to make it easier to save/restore this collection of variables. But note that $domain and $local_part aren't always in an address. Check out when these are set. Note also the new $address_data possibility.
- Spool_in and spool_out - speed up by using a table?
- Find a more compact way of encoding the options interpretation, and also of checking for incompatible options.
- Find a more compact way of passing an open SMTP channel without having to use options. What about the TLS state information? Could use a pipe to pass more data.
- Some people have suggested separately loadable modules. But do all systems have them? Is this going too far for just a few specialist users? In particular, people want to be able to replace the logging with his own code. Can we arrange this without going for the separately loaded modules? (cf the incoming checking code.)
- SIGHUP the daemon - don't close the sockets; instead pass a list of them somewhere for the new daemon to pick up. Iff started by exim or root, of course. There might be quite a long list of them - argv might not be the best idea. If this were done, then a non-setuid exim daemon could be SIGHUPped.
- Parallel deliveries. Currently dead host information doesn't get propagated between them very well. Is there anyway this could be improved?
- In some environments the use of gethostbyname() seems to cause problems. Check out its use, and see if having a "force DNS" option could be helpful. But people would have to know what they were doing.
- accept_max_per_host is a slow, linear search. If smtp_accept_max is large, this can be very slow. Is there some way we can speed this up? Some kind of index based on the IP address? Remember, this is in the daemon, so it must not consume store.
- Look at code in pidentd for running Exim in wait mode from inetd and re-using the socket. This would allow it to run more tidily as non-root.
- Think up some scheme for checking for orphan files in the spool directories. Perhaps -bp should always do it, but it would be nice to have it done automatically now and again. Maybe we just leave this for a cron job? Perhaps a new -bx, e.g. -bpck or something. Better, perhaps, is a separate Perl script. Orphan = a file that is over 24h old (or 1s when test harness) and either doesn't end in -D or -H, or is a -D without a matching -H (or vice versa).
- Swamping with delays in checking for reserved hosts - the connections are counted in the total allowed. Can we improve on this somehow? Maybe shared memory can help here. Think about different states and different limits.
- Lists that must use colons: can we check for other cases, and fix them up before passing them on? Is it worth it?
- Process receiving error message fails - can we get more info, such as the stdout/stderr?
- dbmbuild - if renaming one of .dir/.pag fails, reinstate the other. Should there be a lock?
- Write a script to check for format problems in the source - formats that are not fixed strings and are built from outside code.
- freeze_tell: Don't if message is a bounce message containing From: the local machine - even if the bounce comes from another host.
- Add additional data into the "frozen" log message at end of delivery, e.g. if remote host was the local host or whatever. At least some cross referencing.
- Someone had a requirement to install the Exim binary in a different place to the utilities, etc. Also, for different builds on the same host and architecture.
- Include (part of?) the ppid in the message id? Or a random number?
- Re-implement the code in readconf that reads error names for retry rules. Make it use a table for most of the error types. Then see if we can usefully add any additional error types.
- Should there be "exim -bP acls" etc? It would mean inventing some kind of "hide" facility within the ACL syntax.
- VERY LONG TERM: the message ID is too small now, with the recent changes to cram in the sub-second time. It would be a big project to extend it; Exim would have to recognize both forms for a while, and become stable, before generating the new form. Probably a runtime switch needed. The new form needs at least microsecond time (or more?) and should probably cope with 64-bit pids, just to be safe (or leave expansion space that could be used for that). It should also be able to hold big enough things in base 36.
- Take a look at libexec.
- Sort out the stcncpy/strlcpy issue once and for all. Time things.
- OpenSSL - can we pass an opened file for certificate? Repeatedly? Otherwise pre-initialize while root? There do seem to be functions for manipulating certificates, but documentation is scarce. Can we just load the certificate in as root in the server?
- Consider using poll() to close unwanted fds. Is this efficient? Perhaps it doesn't matter for the daemon.
- On a 64-bit system there are some cast warnings for casting addresses to ints. Either we must find a way of not warning, or we'll have to use unions to get round it.
- Run splint on the source?
- It has been suggested that rejection because not authenticated should use 530 and not 550, but this is hard to detect because of the way ACLs work.
- When there is a sender verify failure, $acl_verify_message contains "sender verify failed", not the details of the failure. Should this change? Some of the waffly details are added later in smtp_in.c. In the ACL that text is in
sender_verified_failed->user_message.
- An empty string for a transport filter currently causes an error. Should it ignore? Tricky because of special expansion rules for commands.
- GFDL for documentation (www.gnu.org/licenses/fdl.html)? The 1.2 version of this licence is still quite new (it is dated November 2002) so I think waiting for reaction/opinion is the best plan. There are Debian concerns about this licence. At very least, no Invariant Sections and no Cover Texts can be used.
- Allow $recipients in other places. Not clear what this value should be if, say, the system filter has overridden them. Default would be envelope recipients, as now.
- Error in transport filter. See test 407. All 3 processes see errors - which one should be noticed? Transport_filter_temp_errors may be needed.
- Think about 5xx thresholds -- too many and you're out. What about 4xx?
- autoreply - should it call /usr/sbin/sendmail? Provide a way of not passing -C and -D when creating the message ('cause it won't be privileged).
- Strings containing \000 - anything we can do?
- Make set_process_info buffer bigger, and put the overflowed message at the end, thereby leaving the start.