Campaigns' sending capabilities regarding MMS are around 25 MMS/second. Although, this is a theorical metric as many factors can impact that sending speed, such as:
Weight of whole message (media, length...)
Amount of contacts
Hours of sending (if too many people are sending campaigns at the same time, the platform can experiment latencies)
What can I do if my MMS campaign take too much time to be sent?
First, wait for the indicated time slot (that was mentioned on the finalize page before sending) to end, it might take longer if there are multiple campaigns sending at the same time. If no message was received by your client base, contact our support for help.