LDAP connections from 389 to random port

[milesteg]

Hi all!

I have the following zimbra configuration:

Edge MTA based on Zimbra <-----> ||Firewall|| <-----> Zimbra Server

I've opened LDAP TCP port (389) in both ways (from zimbra server to MTA and viceversa).

I've detected in my firewall logs that Zimbra Server is trying to open connections from port 389 to a random port in the MTA, I mean:

Source:Zimbra Server:389 ---> Destination: MTA:47116, 47118... and so on (it's trying to establish the connection in a continuous way).

Which could be the cause of this? Is there any way to stop Zimbra Server trying to establish these connections?

Thanks a lot!

[milesteg]

I've done a packet capture, and seen that Zimbra Server is sending RST TCP segments to Zimbra MTA.