IMAP reliability & tuning

[j2b]

I am using Zimbra OSS for quite a while, still learning all new things. I do use it regularly as web client. But recently I got new accounts, who would like at least for beginning, to use their regular Outlook and Mac Mail clients, while whole changeover can be implemented.

When configuring IMAP accounts on MS Office Outlook and Mac Mail, as well as IMAP for iPhones, all went well. BUT...

If you (my customer) expects new mail, and opens his application, he starts to regularly press Send/Receive or Get mail button, to make new checks on servers. As to my notice, following checks take much longer time, than initial one after loading software, but then I noticed, that there is new mail on web client, but it can not be accessed via IMAP client. At least only possibility is to close email client, and after 5-6 minutes open it again. And then these new mails get synchronized. The same is with iPhone. When I resync account within a minute, phone is checking account, but no data get synchronized.

Is this connected with server tuning, as I suppose, that IMAP mail clients work corectly and there is no problem with network configuration and letancy?

If anybody experience similar things, please lead me to position to look for, as at the moment for me it is quite blank field. I do not notice any server (ZCS) overload at that time, and IMAP / POP is configured up to 1000 connections (which probably is too high for current needs).

[phoenix]

There should be no problem with any client getting email via IMAP, it (the client) should poll the server at whatever interval is set in it's configuration or (if the client is using IMAP IDLE) it will update as email arrives at the user mailbox - both of those situations work for me against a Zimbra server using any number of different clients. Apart from that I don't really understand what the problem is, are you saying they don't get the mail or it doesn't arrive at their client or it's slow or what?

[j2b]

Hi, the problem is in not arriving to IMAP client. And first synchronization of IMAP client (when Mail App is launched) is ok, but when hitting Send/Receive/Get mail - next times it takes very long to finish sync job, and no results are returned, despite fact, that there is new e-mail in Inbox, which can bee seen on Web client. No connection errors are thrown out.

My customers say, that they do not receive e-mail (via IMAP client), but in web client it is in the Inbox.