These are the changes from Sunder 2.1 to 2.1a:

Severe Bugfixes:
* Groups were very unstable. Hopefully less so now :) (many people had problems here, the biggest bug)
* declan would crash the mud in some cases. Fixed.
* clan petition join bug - fixed thanks to Dregnus (jholt@acom.us)
* If a socket blocked, it would disconnect the offending user. Fixed.
* Several files were being left open during the boot process. Would show as a crash after numerous copyovers. Fixed.
* Fixed a bug that set a decay timer on any items that went through the "put" command. Woops.

Minor Bugfixes:
* Notification sent possibly to wrong clan on declan and setclan. Fixed.
* Typo command also logs to wiznet bug channel now so online imms can see notices.
* MXP Users can no longer disable colour with colour command There was a reason for this.
* More changes to ignore broken zMud's Pueblo support (MXP is preferred for zMud users)
* Some possible bugs in notication fixed.

Features:
* Intermud-3 (i3) network has been implemented. Edit the config file in i3/ directory.
* clients.c New Functions (neither used in 2.1, but you can find uses for them):
  tag_secure - sends secure line tag for MXP or </xch_mudtext> for pueblo.
  tag_close  - closes secure line or pueblo tag.
* Can now do "wiznet all" to turn on all wiznet events.