When it comes to sending an important document or package, there are various words that can be used instead of "sending by mail". One of the most common alternatives is "mailing", which means to send something through the postal service. Another synonym is "posting", which is often used in British English. "Shipping" is another word that can be used, though it's typically used for larger or more heavy-duty items. "Dispatching" is another option, which implies a sense of urgency or importance. Lastly, "delivering" can be used to indicate that the item is being sent directly to its intended recipient, rather than being sent through the postal service.