Webmail send issue

[ITpro10]

I apologize if this is in the wrong location. Here is a little background.

I work for an IT company that is doing IT support for a charity in the local area. All of my experiance is with MS Exchange, this is my first experiance with Zimbra. The charity we are helping uses zimbra for their email which they get from a local university. They have no on site technical people.

They access their email accounts via web browser. The zimbra mail server is located on the university campus. I have no information on the server specifics.

The issue is that one of the users cannot send from their own specific PC. I understand that this is most likely not a zimbra issue but more of a windows issue, i had no where else to turn.

This issue started after installing a firewall on the network.

The user can login to the email web page, use full functionality of the site, folders, etc. They can even compose a new message. But as soon as they hit "send" the browser just sits. The results are as follows:

IE = Unable to display this webpage
Firefox = Blank white screen, "done" in lower left corner
Chrome = 324 error

This only happens for this one specific user on this one single PC. It does not happen from any other PC. And it only happens with zimbra web mail; gmail, yahoo mail, even our companies own OWA work fine.

I've tried reseting all web browsers, removing temp data, rebuilding the network connection, even tried the winsock fix recommended when google'ing the 324 error. I've also ran reg cleaner and repair tools. Flushed and registered DNS, disabled all AV and firewalls.

I guess my question is, are there any user/PC specific settings that would store anything on the local PC that would be affecting Zimbra web access. Like cookies, or cached data, etc. If not, has anyone with any zimbra experiance heard or seen of this issue before?

Any assistance is greatly appreciated.

Thank you for your time.

[jonallport]

This sounds familiar to something I see occasionally. Questions:

Does ZCS have proper/trusted SSL cert?
Does the mail contain CID/inline images?

I have seen in the past (IE7/8 on WinXP) that the CID content is seen by the browser as 'unencrypted' data on an encrypted page and denies it, stopping the whole process. A quick change to the browser settings fixes it.

Does that fit your scenario?

[ITpro10]

I'll check it out. That does sound like something that could be affecting it. I thought about that but wasn't sure since it wasn't happening on other PCs.

I do know that it does have a valid certificate for the site.

I'm going to be on site shortly. I'll look into it.

Thanks for the response.

[ITpro10]

Update,

yes it does use a CA, its a GeoTrust certificate verified by Equifax Secure CA.

Once I have a resolution I will post incase anyone else runs into this.