Several times reported. When using big list of recipient, the mass message does not work (no message posted on talk page), but does not issue any warning, and no mention in the log either. The sender then wonders if it is just "delayed" or "will never happen". The number above which this happens fluctuate, eg, sometimes the same list of 700 people works and sometimes it does not).
the tool should either send a notification of failure to the sender, or the failure be listed in the log.