Please tell how can I send an email in absence of me, at a desirable
time.
In Outlook, hit F1 and search its help on "delay delivery". The
included help has lots of information on how to use the product.
If you are using Exchange as the mail server, it will send the delayed
mail. However, if you use POP3 or IMAP as the mail server, you will
need to leave Outlook running all the time so it can actually send the
mail at the time you specify (after all, something has to be running
to do the sending).