Web Mail vs Outlook-Activesync vs iPhone-Activesync do not match.

Web Mail vs Outlook-Activesync vs iPhone-Activesync do not match.

I have a new account. I use 3 clients simultaneously: mail.zoho.com, Outlook 2013 (Activesync) and iPhone 6s latest (Activesync).
I deleted all mail in all folders at the beginning of day (including trash/spam) for each of past 3 days.

Issue #1:
I noticed that all 3 do not always stay in sync. There is always 1 or 2 emails that show up in one but not in other.A email I received at 6:50 AM PST shows up on web/outlook but not on iPhone. Two days ago, one email showed up in outlook but not in Web email.

Issue #2:
Often Outlook is out of date for several minutes or hours, if ever updated. I recall one message yesterday visible on web never showed up on outlook for several hours.