After checking, you may have observed that some SMSs in the AMS expire earlier than it would be expected as a result of the configuration for a given Delivery Scheme, and would like to know why this is the case.
The most likely cause for the reported behavior is that the option "Restart On New Message" has been selected in the Delivery Scheme Table:
This will make so that, upon receiving a new message for an MSISDN, the time interval between delivery attempts for older messages will be reset to the first, but the number of attempts will remain at the current value.
To better understand how this works, it's best to consider the example from the table above. Let us assume that the Maximum Attempts have been set to 15 and the Maximum Validity is 12 hours, with an increasing interval between attempts so that the last attempt coincides with the time limit.
Under normal circumstances, SMSs would never expire before the time limit is reached. However, if a new SMS is received for that particular number and the "Restart On New Message" option is checked, the time until the next attempt will again be reduced to the first interval. This can be seen in the attached sample table:
After the 12th attempt, a new message was received for the same number, forcing the next delivery attempt to go back to 5 min, instead of 75. This caused the following attempts to happen much quicker, reaching the 15 delivery attempts much faster than it would have happened otherwise.
Therefore, if you wish to prevent this behavior, you will only need to toggle this option off. Some other things to note regarding the "Restart On New Message" setting are the following:
- This setting is per Delivery Scheme, and there will be no impact from attempts from accounts using a separate Delivery Scheme.
- Changing the setting will not affect existing messages retroactively: old SMSs will be unaffected.