Here's a new release of the patch taht incorporates new features such as:

1) better configuration through config files
2) better implimentation of MySQL map

Here's a couple of points on installation:

1) Go grab sendmail-8.9.3 from ftp.sendmail.org
2) Untar the distribution
3) copy sendmail+mysql-0.2.1beta2.patch into sendmail source tree
4) type "patch -p1 < sendmail+mysql-0.2.1beta2.patch"
5) Edit src/mysql_sendmail.h as follows:
   #define ALIAS_LHS "address" --> replace by what you want
   #define ALIAS_RHS "alias" --> replace by what you want
6) type "make" in the top directory of the source tree
7) type "make install" or copy src/obj.<OS> to your location ex: /usr/sbin 
8) do "chmod +s /usr/sbin/sendmail" if not doing "make install"
9) edit sendmail_mysql.conf to your liking and copy it into /etc (do not
   leave anything blank except MysqlLHSColumn and MysqlRHSColumn when not
   using MySQL map)

If you want to use MySQL map do the following:

1) just after patching the source tree edit src/Makefile.m4 and put the
following(i put it there by default, if dont want to use it, take it out):

# environment definitions (e.g., -D_AIX3)
ENVDEF=       -DMYSQL_MAP ifdef(`confENVDEF', `confENVDEF')

2) when finnished installing edit sendmail_mysql.conf and 
   fill up MysqlLHSColumn and MysqlRHSColumn
3) edit your /etc/sendmail.cf:
   "K<map name> <options>" 
   where options are: 
   1) generic ones like: -N -O -o -f -a -A -t -q -m -T
   2) mysql specific: -H<hostname> -U<username> -P<passwd>
      -D<database name> -M<name of the table for the map>
      -L<LHS field name> -R<RHS field name>
4) create an Ruleset to use with that map ex of mine:

###################################################################
###  Ruleset 98 -- local part of ruleset zero (can be null)     ###
###################################################################

S98
R$+ < $+ . >          $1 < $2 >       remove trailing dots
R$+ < $+ >            $: < > $(domainalias $1$2 $)    match user@address
R< > $+ @ $*          $: < $1 > $(domainalias * @ $2 $)	match*@address
R< $+ > * $*          $: < > $1 $2    replace * with userid
R < $+ > $+           $: < > $2       bugfix
R< > $*                       $: $>3 $1       and rewrite using S3
 
5) create your database:
   Tables:

USERS:

mysql> desc users; <- user table name
+----------+--------------+------+-----+---------+----------------+
| Field    | Type         | Null | Key | Default | Extra          |
+----------+--------------+------+-----+---------+----------------+
| username | char(32)     | YES  |     | NULL    |                |
| passwd   | char(32)     | YES  |     | NULL    |                |
| uid      | mediumint(9) |      | PRI | 0       | auto_increment |
| gid      | mediumint(9) | YES  |     | NULL    |                |
| gecos    | char(32)     | YES  |     | NULL    |                |
| home_dir | char(32)     | YES  |     | NULL    |                |
| shell    | char(32)     | YES  |     | NULL    |                |
| maildrop | char(128)    | YES  |     | NULL    |                |
+----------+--------------+------+-----+---------+----------------+
8 rows in set (0.00 sec)

ALIAS:

mysql> desc alias; <- alias table name
		+---------+-----------+------+-----+---------+-------+
		| Field   | Type      | Null | Key | Default | Extra |
		+---------+-----------+------+-----+---------+-------+
ALIAS_LHS->	| address | char(128) | YES  |     | NULL    |	     |
ALIAS_RHS->	| alias   | char(128) | YES  |     | NULL    |       |
		+---------+-----------+------+-----+---------+-------+
2 rows in set (0.00 sec)

MYSQL_MAP:

mysql> desc domainalias; <- MySQL map table name
	+-------------+-----------+------+-----+---------+-------+
	| Field       | Type      | Null | Key | Default | Extra |
	+-------------+-----------+------+-----+---------+-------+
LHS->	| address     | char(128) | YES  |     | NULL    |       |
RHS->	| domainalias | char(128) | YES  |     | NULL    |       |
	+-------------+-----------+------+-----+---------+-------+
2 rows in set (0.00 sec)


sampe sendmail_mysql.conf:

##############################################################################
# General (can be overriden in sendmail.cf by per map options for MySQL map)
# DO NOT leave blank
##############################################################################

MysqlHost               host
MysqlUsername           user
MysqlPassword           passwd
MysqlDatabase           database_name
MysqlUserTable          users_table_name
MysqlAliasTable         alias_table_name
MysqlMapTable           mysql_map_table_name

##############################################################################
#  For the MySQL MAP only (for alias you have to define it in
# mysql_sendmail.h before you compile) ONLY leave blank if not using MySQL map
##############################################################################

MysqlLHSColumn          LHS_column_name   # Left hand side of the MySQL Map table
MysqlRHSColumn          RHS_column_name   # Left hand side of the MySQL Map table