Saw similar problems during the morning of Wednesday, 19 July, experienced similar problems. Using Mac and MS Entourage to access GMail via POP, got the following errors
entourage error temporary system problem
entourage error 4.7.0 temporary system problem
entourage error 5.7.1 bad or missing rcpt domain 39sm35596wrl
Found no real solutions doing Google searches for these issues. Tried deleting the GMail account from my POP list and reinstalling it. No luck - similar error messages. Tinkered with other solutions from similar problems in the past - such as changing settings and ports - still no luck.
Then, it just started working. Weird.