Dear experts,
In multi-server environment with zimbra proxy (2 mailbox, 1 proxy), the users are using Outlook (POP3/SMTP) for sending/receiving email via Zimbra POP/IMAP Proxy. Everything is good in LAN network but in WAN network, sometime there are some users can not sending/receiving email with the following error:"Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity". The error id: 0x800CCC0F

Are there any settings for optimizing POP/IMAP Proxy via WAN network?

Thanks for your help.