[CentOS] iptables question

The logs on my mail server are filling up with this kind of thing:

Oct 19 17:03:51 bnofmail kernel: REJECT: IN=eth0 OUT= MAC=XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX:XX SRC=195.140.240.6 DST=XX.XX.XX.XX LEN=189 TOS=0x00 PREC=0x00 TTL=52 ID=6284 DF PROTO=TCP SPT=25 DPT=32776 WINDOW=65535 RES=0x00 ACK PSH URGP=0

The source port is always 25 and the destination is a high-numbered port. The destination address is the private IP of the server. These seem to be related to outgoing email connections based on the source IPs, but I don't know why they are not part of an established connection. The mail server seems to be running just fine regardless of these blocked connections.

Any ideas?