Difference between Windows Time Service and Internet Time in Date & Time Properties

When I do a manual time sync in Date & Time properties, sometimes it fails,
and sometimes it succeeds. When it succeeds, it says that the next time
sync will occur in a week. However, later that night I get errors in the
System log that W32TIME was unable to get the time. Event ID 29 & 36. The
next day, the time is off...mostly fast by about 2 minutes. I tried several
different time servers.

Why does Internet Time say the next sync will be in a week but W32TIME tries
to sync that same night? How can I get it to sync properly as this is our
email server and I would like accurate time stamps on our emails.

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Thanks!