Attachment problem

[SMCRuss]

When we receive an attachment and forward it on to another email address our web client stalls out. But if we save the email before sending to the Drafts folder and then open it from from the Drafts folder it will send just fine. What causes that? How do I fix it?

[darioj]

We've had similar issues, zwc randomly stalls while sending, you get a notice that the task is taking too long to complete or a network error.
Then you save to drafts and it sends fine (sometimes).
Check logs (/opt/zimbra/log/mailbox.log), there should be an error in there that might take you in the right direction.

In our case it was caused by a miss configuration of the mta . We've left an old domain in the "Web mail MTA Hostname" (server -> mta tab) which caused the web client to stall occasionally while trying to connect to the nonexistent server fqdn.
The fact that it happened more frequently with attachments led us in the wrong direction.