PPTP VPN not working on Yosemite 10.10.3 with OS X Server 4.1
Sorry for being untechnical, but I solved a VPN/Yosemite issue: After a smaller Upgrade my VPN still connected, but didn’t let anything thru. The Update somehow „unchecked“ System Preferences > Network > VPN(PPTP) > More…/Options > Connecting Option > Send all traffic through VPN Connection (third option in the first list in this dialog; I'm translating/guessing from the german version). Setting it back to let everything go through resolved all issues; Mail, afp, ftp, vnc came back just like that.