If you are using stationery, some default to a specific font and size.

Tools | Options | Compose. Make sure nothing is checked or selected in the
Stationery section.

Also see:

OLEXP: The Font Size Changes When You Press ENTER in a New Message:
http://support.microsoft.com/default...;en-us;Q232001

OLEXP: Default Font Size Is Not Applied in a New HTML E-mail Message:
http://support.microsoft.com/default...;en-us;Q240730

OLEXP: Large or Small Font Printing Message from Outlook Express:
http://support.microsoft.com/default...;en-us;Q276435

OLEXP: Cannot Change Text Format Using Outlook Express:
http://support.microsoft.com/default...;en-us;Q178895

OLEXP: Large Font Printing Message from Outlook Express:
http://support.microsoft.com/default...;EN-US;q276435
--
Bruce Hagen
MS-MVP Outlook Express
~IB-CA~

"History Fan" wrote in message
...
My PC: desktop running XP Home SP2. Outlook Express 6 SP2 is my
email and newsgroup program. DSL connection.

Just today, while composing some email messages, I noticed that I
cannot change the font size. It always stays at size "12." Every other
editing option (centering, bold, underlining) works fine. I create a new
message, type some text, highlight a word, or words, select the font drop
down arrow, select a larger number, but it defaults back to "12." Any
suggestions?