Use a specific subject, state your purpose early and finish with the action needed. Keep the tone polite and leave out unrelated details.
Practical examples
I am writing to confirm our appointment.
أكتب لتأكيد موعدنا.
Please find the revised schedule attached.
تجد الجدول المعدّل مرفقًا.
Could you confirm by Thursday?
هل يمكنك التأكيد بحلول الخميس؟