Secret Missions:
     Enter  the  following Wonder Mail passwords to obtain some secret
missions.  These  codes  work with either version of the game, but you
must have access to the mission's dungeon for them to work.

Meet with Minun:
Enter f?rpf?...??+7?ct?h64?0r??? as a password. 
The reward is a 400 Poke and a Heal Ribbon. 
Note the ellipse (...) is entered as a single character, not three.

I'm So Worried About Ninoran:
Enter 1??94wt?0f9jnf?97770+8?w as a password. The reward is 500 Poke.

Voltorb's Accident:
Enter 4?mf87t??3n4[Female]r?2-?6r8c?? as a password. 
The reward is a Max Elixir. 
[Female] refers to the single-character female sign.

Help I Can't Exit:
Enter ??-fh?f??3p?q??+8?76T8?? as a password. 
The reward is TM 31 and 200 Poke.

Find Wigglytuff:
Enter ??-FH?F??3P?Q??+8?76t8?? as a password. 
Not sure about this reward.

Blue Plains Friend Area mission:
Enter 5?2YQW0??T0QJC?[Male]FH16WR?W as a password. 
[Male] refers to the male sign, a single character. 
The mission will allow you access to the Blue Plains friend area.

Stormy Sea mission:
Enter X??S??X?468?*+??9756SY?? as a password. 
The quest rewards you with 400 poke and a magicarp (blue version) 
or a trawl orb and a feebas (red version).

Weavile statue:
Enter ??F(...) [Male]2S? 4R73 S0?7 64NR J7?W as a password.