canread

Canread is a functionality of the Internet Message Access Protocol (IMAP) and the Simple Mail Transfer Protocol (SMTP) that allows clients or users to determine whether a specified message or message body part can be read by a given user.

In IMAP, canread is used in conjunction with the COPY command to copy a message to the specified mailbox, while in SMTP, it is used in the STORE command to modify the flags of a mailbox without permanently removing the message.

The canread functionality is typically used when a user requests to read a non-public message, such as a meeting request without a visible time, or a message without visible contents. The client requests whether the server can read the message, and the server responds with a message stating whether the message can be read or not.

canread is not related to the permissions of the mailbox owner but to the read permissions of the sender. If the message was sent to a specific distribution group or cc recipients where not all have access to it, canread will return false, even though the owner has full access to the mailbox.

Canread is also used to improve performance when searching messages and flag combinations to save access time on the server and over the network by doing away with the need for a full read of the message when only the message size and if it was readable will be needed.

It is essential to note that the specification canread functionality is in continuation with ongoing accident with IMAP, which was first defined and published in 1986.