Content channels for electronic messaging

One or more computer-readable storage media comprising instructions that, when executed by one or more devices of a messaging system, cause the one or more devices to:

• output a messaging user interface having a designated portion to enable interaction with content channels, the designated portion configured to display an item corresponding to a particular content channel that is distributed to the one or more devices as an electronic message and to which a user has previously subscribed;
• detect an update that is available for the particular content channel (510);
• and
• update the messaging user interface to reflect the availability of the update by exposing an indication of the available update with the item in the designated portion.

A method performed using one or more computing devices of an electronic messaging system, the method comprising:

• distributing, to one or more clients, an electronic message including a content channel configured to integrate multiple content portions of different types and define arrangement of the multiple content portions one to another, the electronic message having data to enable each of the one or more clients to:
• ascertain that the electronic message includes the content channel;
• and
• present the electronic message in an inbox of a respective messaging user interface with an identifier to identify the presence of the content channel and selectable to pin the content channel as an item in a designated portion of the respective messaging user interface;
• detecting that an update is available for the content channel;
• and
• communicating the update to at least some of the one or more clients to cause an indication of the available update for the content channel to be exposed with the item in the designated portions of the respective messaging user interfaces.