please enclose literal values (like gconf values) in double quotes.

http://live.gnome.org/TranslationProject/DevGuidelines/Enclose_literal_values_in_double_quotes

#: ../plugins/mail-notification/apps-evolution-mail-notification.schemas.in.h:6
"If true, then beep, otherwise will play sound file when new messages arrive."

#: ../mail/evolution-mail.schemas.in.h:115
"Specifies the header to check for junk. The format is headername=value in 
gconf."

#: ../mail/evolution-mail.schemas.in.h:129
"This key is read only once and reset to false after read. This unselects the 
mail in the list and removes the preview for that folder."

#: ../mail/evolution-mail.schemas.in.h:68
"Load images for HTML messages over http(s). Possible values are: 0 - Never 
load images off the net. 1 - Load images in messages from contacts. 2 - 
Always load images off the net."

#: ../mail/evolution-mail.schemas.in.h:126
"This can have three possible values. 0 for errors. 1 for warnings. 2 for 
debug messages."