gnus: Diary Group Parameters
6.8.2.4 Diary Group Parameters
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When you create a new diary group, or visit one, ‘gnus-diary’
automatically checks your group parameters and if needed, sets the
summary line format to the diary-specific value, installs the
diary-specific sorting functions, and also adds the different
‘X-Diary-*’ headers to the group’s posting-style. It is then easier to
send a diary message, because if you use ‘C-u a’ or ‘C-u m’ on a diary
group to prepare a message, these headers will be inserted automatically
(although not filled with proper values yet).