Syncing Adroid phone to laptop

[#1]

For some reason lost sync from Android phone with my laptop.  Followed the instructions to restore, but encountered a problem with Outgoing Server settings, with the instruction to 'try updating port and/or security type'.  What should I be doing in response to this?

[#2]

Is your phone connected to a mobile network or to your router? If it's mobile you will need to set up authentication to be able to use relay.plus.net. The username and password for this will be the same as you use for incoming emails; SSL should be no/off. Using port number 587 on relay.plus.net is recommended (though 25 should work).

[#3]

Thanks Spraxyt.  Connection is via mobile network.  Now here's the thing: in Settings/Accounts, both Personal (POP3) and Email (Gmail) show that they were last synced today.  However, I keep getting push notifications that my Gmail connection failed, and sending a test to my laptop likewise fails.  Don't understand why one moment everything was OK, and the next I have this situation.