Setting up email on Nexus 7

[#1]

I had a few problems with my Nexus 7 tablet so thought returning to factory settings would help.  Beginning to wish now that I hadnt come up with that idea!  I cant get my plusnet email account set up.  I'm carefully following the guidance on the plus net site, but after adding in the incoming server settings (IMAP) all I get is a message saying "Couldn't open connection to server".  The specified port is 143.  Any suggestions?
The back up of gmail isnt any better - that's been stuck on "Waiting for sync" for a couple of hours now.  I've checked that "auto-sync data" is on, but that hasnt helped.

[#2]

Remember Plusnet's email doesn't use encryption, so make sure that option isn't enabled.

[#3]

No it's not that  - looked in settings and have checked that it isnt encrypted.

[#4]

Does the Nexus connect OK to your router? Does browsing work?

[#5]

Yes - I'd checked that out.  I tried to set up emails again this morning and all worked OK.  I didn't do anything different - perhaps it was just an intermittent problem with the broadband connection.
Thanks for the replies