To send events we are using an " esp32-wrover e" microcontroller. The transmission for single notifications works and takes approximately 30 sec. If there is more than one event it will only dispatch the first event. The other messages get lost. We have noticed, that the microcontroller is responsible fort this behavior.
Is there a possibility that Icinga2 buffers notifications?
Is there a possibility that Icinga2 sends time-delayed notifications?
From the architecture of Icinga I don’t think it makes sense to buffer the messages in Icinga but nothing is stopping you of putting a buffer in between Icinga and your SMS sender, that can only manage one at a time.
We use SMSEagles and a self written loadbalancer and queuing application if front of them.
But in your situation, I would alter the SMS notification, so that it writes files to a temp folder and have a script triggered by a systemd timer or inotify that loops over the temp folder, tries to send one message at a time and deletes the files on success.