I’m looking for a way to change the default value

It's better to ask plugin (Out Of Office) author to achieve this feature.

P.S. Out Of Office plugin doesn't work with Thunderbird 12.

I understand that If I add :days 1 to the sieve script, The auto message will be generated once per day. However, the users are not sophisticated enough to alter the script (they use a simple GUI in Thunderbird). I’m looking for a way to change the default value, since the parameter is not set via the GUI, it will default to 1….if this is possible?

“4.1. Days Parameter

   The ":days" argument is used to specify the period in which addresses
   are kept and are not responded to, and is always specified in days.
   The minimum value used for this parameter is normally 1.  Sites MAY
   define a different minimum value as long as the minimum is greater
   than 0.  Sites MAY also define a maximum days value, which MUST be
   greater than 7, and SHOULD be greater than 30.

If ":days" is omitted, the default value is either 7 or the minimum
   value (as defined above), whichever is greater.”

P.S.
- Roundcube webmail has this feature (with official plugin "managesieve").
- iRedAdmin-Pro-LDAP-1.6.3 is out-of-date, it's recommended to upgrade to the latest v1.7.2. Upgrade iRedMail first, then upgrade iRedAdmin-Pro.

Clients connect via Thunderbird (only), and the vacation notification works (Sieve & Out of Office addons). When users create a vacation message, the days parameter is not set; and therefore, defaults to 7. Does anyone know how to change the Sieve default for the days parameter to 1?

Thanks,
Mark