This occurs when an email is sent to a receiving mail server using SMTP (Simple Mail Transfer Protocol). The receiving mail server then decides whether or not to accept the message. "Delivery" refers to the acceptance or not of the message by the server.
This occurs before the message is placed in the inbox or spam folder.
Email delivery is extremely important, especially when the emails sent are vital in importance to the company, such as the return of keys or passwords, status notices, and impending alarms. This is because if the emails land in the spam or junk mail folder, they will be of no use to either the customers or the person who sent them.
To answer the question of when an email is considered "delivered", there are several different answers. Here are three of the most common answers to this question.
An email is considered to have been delivered when:
This can be compared to sending an envelope or package to the package receiving room of a building with multiple departments and offices. In the reception room, surely a person signs that the package was received, but this does not mean that the person to whom it was sent received it.
Utilizing the example mentioned above, this would be like sending an envelope or package to a package receiving room, ensuring that someone signs the package, and then delivering the package to the person it was sent to. Whether or not the person opens the package is not taken into account here.
As seen in the 3 cases mentioned, the meaning of "delivered" changes according to the context, the email service provider, and the current situation, and all three answers would be correct. But from a technical point of view, there is only one correct answer.
250 OK Status: to be sure that an email was delivered or not, from a technical point of view, a message is considered delivered when the sending mail server receives an SMTP response "250 OK" when an SMTP transmission is concluded.
A response message from the server of "250 OK" means that the SMTP communication was successful and is relayed in response to every supported command, possibly 4-6 times for each message.
The person sending the email will seldom notice the response “250 OK, as this code is displayed in the background after an SMTP email delivery broadcast. So a message can be considered delivered when it reaches the destination inbox.