Evolution PopUP: Error while Fetching Mail

[SYNass IT Ubuntu / Linux]

Hello Evo users
Recently my Evo 2.12.1 brings this error message also saying:
Host lookup failed: pop.domainname.net: Name or service not known

Why ???

It started with my previous ISP and continues, just changed these days,
with 
the new ISP !

Well, my old ISP used POP, where the new on uses MAIL !?
Well, generally both are used for POP(3) and should not give any
problems !?

I have setup about a dozen accounts some with "alias" resp. "forwarders"
for some 
used nicks ;-)

3 accounts are NOT suppose to remember the PWD due their larger volumes:
I set the PWD manually after reading all the more important personal
emails ;-)

Any hints or suggestions are very welcome ;-))

TIA, cheers, svobi