If you plan to create an autoresponding SMS service,
you should give a thought to the scenario depicted in Figure 1 and described
below. The scenario shows that an endless message loop can occur in case
of two autoresponding messaging applications start to talk to each other.
This message loop can cost a lot of money, because it is often unnoticed by
the operators of the autoresponding services. The good news is that Ozeki NG
SMS Gateway has built in message loop prevention to
make sure you don't run into this situation. On this page you can read about
the message loop threat an the message loop prevention feature of Ozeki NG SMS
The message loop threat can occur in case two autoresponding messaging
applications start to talk with each other. An automatic responses sent
from one system can trigger
a response on the other causing an endless loop of messages, and a huge cost on
the mobile phone bill (Figure 1).
A loop is often started by an unaware human user, who may send
an SMS message using an SMS service, that can also reply to incoming messages.
It is called "Other autoresponding SMS application in the figure above. The
message will be delivered to the autoresponding service (possibly hosted by
This autoresponding service will generate a response and send
it to the other autoresponding service, which - not interpreting the reply
message - will send an error message to the reply, to which Ozeki NG - SMS Gateway may
send an error message, and so on. This will create an endless loop, which may
continue until one of the services is stopped and the phone number or a range of phone
numbers of the recipient is barred.
The endless loop between two services may cause huge costs
because of the enormous number of SMS messages that may be sent.
Ozeki NG SMS Gateway solution
To prevent such message loops, Ozeki NG SMS Gateway has a built in message loop
prevention. This works the following way: Ozeki NG SMS Gateway
registers outgoing messages. If the same text
is sent to the same recipient phone number more then ten times in one hour,
Ozeki NG SMS Gateway prevents message delivery to stop a possible message loop.
How to disable message loop prevention
In some cases the user might want to disable message loop prevention. This is
possible by opening the "Server preferences" form in the "Edit menu" in Ozeki
NG SMS Gateway (Figure 2).
On the server preferences form, click on the "Advanced" tab. In the advanced tab
you need to uncheck the "Prevent message loops caused by autoresponding services"
checkbox (Figure 3).
Please disable this feature with care. If you disable it, you must handle this
possible threat some other way.