When a client sends a long SMS over SMPP, the message is split into multiple parts before transmission. The platform collects all parts before forwarding them to the aggregator – this ensures the recipient receives a complete message rather than a fragment.
When a multipart SMS arrives via SMPP, the platform holds all received parts in a queue and waits until the full set is collected. Only once all parts are present does it send them together as a single message.
If the expected number of parts never arrives – for example, a 4-part message where only 3 parts reach the platform – the message is not forwarded. The incomplete parts remain in the queue until the missing part arrives or the entry times out.
This behaviour means that occasional gaps in delivery reports are not always a routing issue. If a client reports that a message was sent but no DLR has been received, the reason may be that the platform is still waiting for a missing part. The message has not failed – it is queued and will be sent automatically once the final part arrives.
To monitor the current state of incomplete multipart messages, go to Current traffic → Queue of SMS.
The queue shows all SMS parts currently being held, including how many parts have arrived and how many are still expected. Once a message is complete, it is sent immediately and removed from the queue automatically.
