[exim] Queue very slow

# exim --versionExim version 4.87 #1 built 26-May-2016 11:07:39
on a CentOS VPS.I noticed a very slow response with exim -bpc (for example).
I noticed this:
root@server:/var/spool/exim/input# time find . -type f./W/1cBgAW-004C53-1W-D./W/hdr.189271./W/1cCn0W-000jJy-VL-J./W/1cCn0W-000jJy-VL-D./W/1cCn0W-000jJy-VL-H./W/1cBgAW-004C53-1W-H./c/1Vddmc-0006bD-V3-D./c/1aYEzc-003wC1-NN-938896-K./z/1cBpvz-003BKc-Mw-H./z/hdr.195520./z/1cBpvz-003BKc-Mw-D./z/hdr.9495./z/1cCeQz-0022Jj-9B-H./z/1WCnHz-0002T9-Hn-D./z/1cCeQz-0022Jj-9B-D./F/1bOhVF-000ef8-6A-D./F/hdr.156310./x/1WKxVx-002UaG-Qh-D./x/1cC8jx-001MC2-TC-H./x/1WKxVx-002UaH-Qr-D./x/1cC8jx-001MC2-TC-D./x/hdr.594225./x/1WKxVx-002UZf-Io-D./U/1cBQPU-002Eic-0r-H./U/1cBQPU-002Eic-0r-D./B/1VddmB-0006WS-NU-D./B/1cCSlB-003Rqi-PR-H./B/1cCSlB-003Rqi-PR-D........../0/1WKxW0-002ess-GC-D./0/1WKxW0-002UZJ-L4-D./0/1WKxW0-002UYz-Ja-D./0/1cBbM0-0029R4-1U-D./0/1WKxW0-002fAG-9o-D./w/1cCoEw-000AsV-3m-H./w/1cCoEw-000AsV-3m-D./w/1cCoEw-000AsV-3m-J./p/hdr.174654./3/1WKxW3-002Ubm-7s-D./3/1aT7n3-000pIJ-2s-D./I/1VddmI-0006XQ-Ad-D./I/hdr.9031./I/1XP5iI-001R3G-K5-342363-K./I/1XP5DI-000pqL-I2-199351-K./Q/1cBwfQ-001A4T-Rp-D./Q/1cBwfQ-001A4T-Rp-H./g/1TYaMg-0004BG-8t-D./g/1VqhYg-00052O-8S-23356-K./g/1cCmsg-000gso-UV-D./g/1VqhYg-00052O-8S-23391-K./g/1cCmsg-000gso-UV-J./g/1VqhYg-00052O-8S-23402-K./g/1cCmsg-000gso-UV-H./N/1cClzN-000Qhe-Sx-H./N/1cClzN-000Qhe-Sx-D./N/1cCNeN-001nMv-B3-H./N/1Zye1N-001A5o-Ey-D./N/1cCNeN-001nMv-B3-D./N/hdr.192629./N/hdr.203597
real    1m11.889s <==========================user    0m0.000ssys     0m0.081s
What are "hdr.xxxxxx" files?How can I check if queue is corrupted?Anyway, exim -bpc returns 88 messages in queueThank you very much