[exim] Exim down

Hi,

I have a problem with exim and i don't understand what happened.
During one day, mails don't arrive in my application and i can't determine if it s an exim problem or other.
Could you tell me where are stored incoming mails in exim?
In my logs when system work correctly i saw incoming and outgoing mails but when there were a problem I had that :
2012-02-11 21:34:14 End queue run: pid=27054
2012-02-11 21:44:14 Start queue run: pid=28384
2012-02-11 21:44:14 End queue run: pid=28384
2012-02-11 22:15:00 exim 4.67 daemon started: pid=2467, -q10m, listening for SMTP on port 2525 (IPv4)
2012-02-11 22:15:01 Start queue run: pid=2468
2012-02-11 22:15:01 End queue run: pid=2468
2012-02-11 22:25:00 Start queue run: pid=3712
2012-02-11 22:25:00 End queue run: pid=3712
2012-02-11 22:35:00 Start queue run: pid=4796
2012-02-11 22:35:00 End queue run: pid=4796
2012-02-11 22:45:00 Start queue run: pid=5871
2012-02-11 22:45:00 End queue run: pid=5871
2012-02-11 22:55:00 Start queue run: pid=6961
2012-02-11 22:55:00 End queue run: pid=6961
2012-02-11 23:05:00 Start queue run: pid=8200
2012-02-11 23:05:00 End queue run: pid=8200
2012-02-11 23:15:00 Start queue run: pid=9275
2012-02-11 23:15:00 End queue run: pid=9275
2012-02-11 23:25:00 Start queue run: pid=10351
2012-02-11 23:25:00 End queue run: pid=10351
2012-02-11 23:35:00 Start queue run: pid=11600
2012-02-11 23:35:00 End queue run: pid=11600
2012-02-11 23:44:59 Start queue run: pid=12678
2012-02-11 23:44:59 End queue run: pid=12678
2012-02-11 23:54:59 Start queue run: pid=13754
2012-02-11 23:54:59 End queue run: pid=13754
2012-02-12 00:04:59 Start queue run: pid=14992
2012-02-12 00:04:59 End queue run: pid=14992
Could you explain me what is mean?
Cordially,
Marion