Mozilla Thunderbird 2.0x under Mac OS X has the disadvantage that it can not use the integrated address book. This version can use the Mac OS X Adress Book with LDAP. The Patch for this is from Mozilla Bugzilla. IMPORTANT: READ THE RELEASE NOTES
Tortoise Mail is a POP3 and SMTP E-Mail Client written in PHP. By using PEAR Package DB, it supports many SQL-Based Databases (dbase, fbsql, ibase, ifx, msql, mssql, mysql, oci8, odbc, pgsql, sqlite, sybase). It is also PHP 5.x compatible.