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[Russ Kepler <address@concealed>]

I'm having an odd problem on my install.  It's a current release upgraded a 
couple of times using rpms, running with mysql managing the users.  On 
occasion a message is rejected:

May 18 09:18:11 main sympa[12163]: Processing message for modeleng-list with 
priority 5, <002901c31d51$268c6f00$6701a8c0@mainline2>
May 18 09:18:11 main sympa[12163]: Message for modeleng-list from 
address@concealed rejected() because sender not allowed
May 18 09:18:11 main sympa[12163]: Moving bad file 
modeleng-list.1053271087.23355 to bad/
May 18 09:20:22 main sympa[12163]: Processing message for modeleng-list with 
priority 5, <002e01c31d51$774dcdd0$6701a8c0@mainline2>
May 18 09:20:28 main sympa[12163]: Message for modeleng-list from 
address@concealed accepted (6 seconds, 19 sessions), size=2412

This doesn't happen to all users so far as I know, and it seems fairly random 
in the selection of users but with one it seems to be rejecting most of his 
messages.  Any ideas on how to proceed with debugging this?