It happens occasionally that a user will get email notification that they have a new message (notification includes the text of the message), but when they go to the uddeim inbox, there is nothing there. When I check the database, the message is not there either. We know that a message was sent because of the notification. Do you have some idea of what might be happening to these messages/database entries?

Using Joomla 2.5.28 / uddeIM 3.2

It is only brought to my attention when users write to me to ask why they get notification but there is no message. In this case, they have not removed anything. They get notification that they have a message, they login, and they find nothing in their inbox. They write to me, I investigate by searching in the database and find nothing. It seems that notification is happening but the message is not being written to the database. Does that make sense from how the information is handled in the system? Is it possible that a notification can be sent but that the message somehow does not get saved to the database? If so, what would cause this and can I do something about it?

Well, uddeIM does not remove or delete messages when not both, the sender and the recipient, have deleted the message. Before a message is removed from the database it is kept there for a certain period of time that can be configured in uddeIM backend.

Are you sure that they get a new message notification? There is a second notification, the "forget me not" message, that is sent to the users after a configurable period of time when there is a still unread message in the recipients inbox.

It is technical not possible that a new message notification is send and a message is not stored except there is an error in your database that trashes the message without returning any error.

The cases I am reporting are on first time notifications. We process dozens of messages each day without incident. What kind of database error would lead to this outcome 1 out of maybe 1000 messages (meaning, most messages are processed properly, only a few have this problem)?

Don't know, maybe there is to much load and does not accept further commands?

Fact is that a notification message is sent after the SQL command that saves the message has been processed.