I also want to know what solution is there,Thanls.

Me to please!  Be good to set a reminder for sending invoices

You could use the trigger after open from the options menu of the database (tab next to the Data model)

Could use something like this:

let z := (select Invoices where Date + 21 > today());
let i := join(z.Invoicenumber, "
");
let result := dialog("These Invoices are overdue. Do you want to mail?", i, ["Yes", "No", "Cancel"]);
if result = "Yes" then
alert("You pressed Yes and an email will be send")
else
if result = "No" then
alert("You pressed No and nothing will happen")
else
if result = "Cancel" then void end
end
end

This code must be altered to your situation but you get an idea of it.

Steven

The send multiple part is discussed here:

https://ninox.com/en/forum/technical-help-5ab8fe445fe2b42b7dd39ee7/send-e-mail-to-multiple-users-5c59c18ec9c7d05c87e05e62