The main advantages of email are

Speed, low cost and easy record keeping together make up the main advantages of email, and every one of them holds.

Speed means a message can reach the recipient within seconds across the globe.

Cost is low since sending mail online avoids postage and paper.

Record keeping is easy because sent and received messages stay stored and searchable.

Email also lets one message go to many recipients at once with attachments.

These strengths made email one of the earliest mass uses of the internet.