OE does occasionally give "pop-up" notices, but usually with a failed delivery it's a return email, with the original message that you sent as an attachment. The difference may hinge on whether the error occurs internal to your own machine, at your own email provider's server, or from the recipient's server (or an intermediate server between the end points).

The pop-up notices usually have a "cancel" or "close" button somewhere on the face of the window, or like most windows, an "X" at the top right that you can click to close the message. If you sent a large bunch of messages all with the same problem, you may be getting a large sequence of "error reports" that could make it look like one that's refusing to be cancelled. When you close one, the next one is waiting in line to pop up.

The notice that probably irritates me most is the one that says something like "an error has occured, click for complete description" and when you click all you get is a blank window. On my primitive connection, the error message often pops up before the dial-up has finished negotiating the connection, so it isn't an error, nothing is wrong, but OE just likes to brag. Just a case of premature e... $#%#@%

John