In other words, the encryption takes place between individual SMTP relays, not between the sender and the recipient. This has both good and bad consequences. A key positive trait of transport layer encryption is that users do not need to do or change anything; the encryption automatically occurs when they send email.
In essence, the encryption occurs between intermediate SMTP servers, rather than directly between the sender and receiver. This has both favorable and unfavorable effects. A significant advantage of transport layer encryption is that users do not need to take any action or make changes; the encryption happens automatically whenever they send email.