All known PMS for Joomla store messages as plain text in the database, so when you backup your database or use phpMyAdmin you can read all messages without any problems.
When you "obfuscate" a message, this message is encrypted in the database using a key the admin configures in the backend. It is a little bit like ROT13 (see
en.wikipedia.org/wiki/Rot13
), so a human user cannot read the massage but since the key is known the admin could decrypt the message with some effort.
When you "encrypt" a message, this message is encrypted with a key the user enters in the frontend (it is called "password" in the frontend which is actually wrong because it is a key but users usually do not know the difference so it is easier for them to understand what to do). Since this key is only known by the sender and the receiver the admin cannot decrypt the mssage (with major effort it is possible because uddeIM does actually not support strong encryption like AES (symmetric) or RSA (asymmetric) but maybe I add strong encryption in future
)