How do I prevent my Samsung Galaxy S5 from checking my e-mail when I use a public Wi-Fi hotspot?

[4232jl]

I have a Samsung Galaxy S5 phone, and would like to find out how to suppress the regular checking of e-mail when my phone connects via unencrypted Wi-Fi (in such places as libraries or restaurants).

When the phone was first set up in-store, there was a checkbox next to "sync email," which I checked.  (I can also access this checkbox via settings > manage accounts > (account name) > sync settings.)  Checking this box makes the phone retrieve e-mail from my ISP's mail server regularly.  But if I clear the checkbox, then the phone does not check e-mail at all, even when I open the Email app and touch the reload/refresh icon.

Is there a way either to:

• check e-mail only on-demand (i.e. I must open the Email app and then, as an added layer of protection, touch "load more emails" or the refresh icon before it ever will authenticate with my ISP's mail server)
• or, even better, check e-mail only when connected via WPA2-encrypted Wi-Fi or mobile data (LTE) but never send the password over the airwaves when I access a public Wi-Fi hotspot?

[bearone21]

whatever interval you set for checking email, follows that protocol wherever you connect, home or public wi-fi..

I set max/2 hr interval, go into the account/refresh

[4232jl]

How do I set it so that it will check e-mail, but only when I go into the account/refresh?

I don't want it to check the account from public wi-fi at all.

[GalaxyClass]

Turn off your Wi-fi when in a public hot spot, and I do the same 2 hr interval check.

[4232jl]

It would be nice if there was a user-configurable preference to allow certain network activities (such as logging into an IMAP or POP server) only when the connection is secure (as it is with WPA2 and, I assume with LTE mobile data) and not when a connection is wide-open.

There is a setting to "sync email," which I can uncheck, but unchecking that box seems to completely stop the e-mail app from retrieving messages, even when I refresh.  Is unchecking that box before connecting to the hotspot (and then checking it again when I get home) the best that I can do?  (If so, that is just as easy as not using the public Wi-Fi hotspot at all.)

Verizon's 1GB plan is affordable, and I use public Wi-Fi hotspots specifically to avoid overages.  I guess there is a trade-off between saving money and privacy, but there should still be a way to get the e-mail program only to access the network when I tell it to.

[bearone21]

that's why i refresh between the 2 hour intervals....i personally don't ever use public wi-fi.