Win Server 2012 R2
The same situation happen with me and this affects only emails sent and received in SM Webmail.
The daylight change occurred days ago, but the setting in Windows for "Automatically adjust clock for Daylight Saving Time" was NOT checked / active, so after I checked that option the emails sent and received in the SM Webmail still display the old time. Left the server alone for a couple hours until I could restart the SM Service.
And after I restarted the SM Service the correct time was applied.
So I can only speculate that the SM Service only checks for the current server time when we starts (by manual mode or restarting the server).
Anyway just wanted to leave this feedback for future reference.