cannot access emails via iphone though can on samsung!

[#1]

Constantly getting error message imap.plus.net is not responding on iphone, please check settings.  they have not been altered and can receive emails on pc or husbands Samsung galaxy, any ideas?

[#2]

I have seen the iPhone email app unable to receive emails as you describe.  Sometimes it is because the phone has no Internet connectivity, other occasions because the program is borked!
For the latter, unloading email and restarting it fixes the problem.  Go to the main screen, 'expose' the running programs bar, touch and 'hold' the email icon until the icons wiggle and then touch the Red Cross.  Start email again and all should be ok.

[#3]

Sometimes the iPhone loses touch with its email settings.
The way to deal with it is to delete the offending email account and re-enter. Do this by:-
Settings
Mail, Contacts, Calendars
Then select the appropriate account
And hit 'Delete Account'
Re-enter the account details by setting up a new account thru 'Add Account'!
That should take care of it.