Q: SMTP offline not able to send or receive email

I have not been able to send or receive email on my MAC for about a week.I have contacted my provider (Verizon) and have confirmed all required settings are correct. I am able to send and receive email from this account on my iPhone. I continue to see (for no apparent reason) a message which says my server is offline when I am connected to the internet. Taking accounts online when prompted has no effect. I allow Apple to install updates automatically - I wonder if this has been the result of a recent software update? Any suggestions?