log entries are missing when executing api /api2/json/nodes/{node}/journal

[TkT]

I use this api to read the log to get information about when the emails where sent and the status of the emails. But entries missing from this log.
For instance I miss postfix/smtp entries. When i look up the missing email entries in the tracking center I see the postfix/smtp entries
Even when I have only 2 seconds difference between since and until parameters the journal does not return the missing postfix/smtp entries.