Canned replies
If you type the same thing often, save it as a template with a title and body. While replying you pick the template and send — no retyping.
Automatic greeting
A greeting can be sent automatically the first time a customer writes — something like “we have received your request”.
Outside working hours
If you set working hours, messages arriving outside them get a different text — “we will reply from 9am tomorrow”, say. The request is still recorded; the customer simply knows to expect a wait.
Send queue
Outgoing messages are queued and sent in sequence, which keeps the number from being blocked for sending too many at once.