Package: smail Version: 3.1.29.1-14 Under certain obscure circumstances Smail can lose mail:
When it needs to send a bounce message it reinvokes itself with the `-bS' flag, meaning to read SMTP commands from standard input but not to produce responses. It then feeds an SMTP `session' to the subprocess. Now, smail never produces error responses to syntactically valid input (unlike, for example, some sendmails which will fail a RCPT TO on a user that they think is local to them but is unknown). However, the subprocess may fail for some other reason. Perhaps the copy of Smail it wishes to reinvoke cannot be found, or has some configuration error serious enough to cause it to fail to write the message anywhere. In this case the parent smail will write the message into its child anyway and fail to notice the non-zero exit status. I have reproduced the problem with a test setup under controlled conditions, and can provide strace logs &c. I'm not sure what happens if the disk is full. Ian.