This function sends all of the outgoing mail from Exim's queue for an email account.
Note:
To set Exim to queue all outgoing mail for an email account, use the UAPI Email::hold_outgoing function.
uapi --output=jsonpretty \ --user=username \ Email \ release_outgoing \ email='username@example.com'
{- "apiversion": 3,
 - "func": "release_outgoing",
 - "module": "Email",
 - "result": {
- "data": null,
 - "errors": null,
 - "messages": null,
 - "metadata": { },
 - "status": 1,
 - "warnings": null
 
} 
}