Emails has been kept in draft and outbound

It's not only send function, also check new emails sync is not working until restart.
Maybe is it happening because I started to use Viscosity VPN?

It sounds likely if it happened at the same time. If you are not on the latest test release: Hold down ⌥ when clicking “Check Now” in the Software Update preferences pane.

If it is still a problem:

• Open the Activity Viewer when it is still working. (⌥⌘0)
• When it has stopped synchronizing/sending then use “Help ▸ Send Server Logs” to send me the relevant logs.

Keep an eye on the state of the account(s) under SOURCES. When something is offline then it should be indicated by a grey color and a “state” in parenthesis of the mailbox names.

I sent to you the server log.
It happens when I connect to VPN through Viscosity app, Mailmate can't sync. If I disconnect from VPN, it sends normally.

Benny,

I think it's happening not only when I connect and disconnect from the VPN. I keep Mailmail opened all the time, in the end of the day my Macbook goes to sleep. In the next morning when I wake up the Macbook, Mailmail already running and cannot sync until restart.