Digital Engagement: Rules for SMS and Facebook Messaging channels

• SMS:  An agent may enter approximately 840 characters in the text field— these texts will be split into messages of 160 characters each. Although Messaging operates to telecommunication standards, telecommunications carriers do not guarantee that messages will be received in the order in which they are sent.
• Facebook Messenger: Messages are limited to approx 2000 characters. Only 1 message may be sent at a time.

Outbound Messages Timing: ​

• SMS: Agents can send outbound messages to phone numbers at any time as long as the phone number has not been opted out. 
• Facebook Messenger: Outbound without a recent inbound initiated message is not generally available at this time -- this is a beta feature, only available for customers that enrolled in the pilot agent-initiated outbound messaging. For general customers, outbound messages can only be sent within 24 hours after the last message from the customer. After 24 hours the conversation is closed and the agent will have to wait for another message from the customer before they can reconnect. The time limit does not honor business hours. 

• SMS: Messages can still be sent to customers even if the customer has deleted the thread. 
• Facebook Messenger: If a customer deletes or archives the conversation, the connection is closed and the agent will have to wait until the customer messages in again. 

Searching / AutoLinking: 

• SMS: Messaging searches based upon the phone number. 
• Facebook: Messaging searches based upon the First and Last Name of the customer. In Orgs with many Contacts/Leads, this could slow down the search, and "searching with Unique ID" is recommended instead. 

See also:
Considerations for Text Messaging
Considerations for Facebook Messenger
Start a conversation with a customer