Wondering what the packet loss to fastmail is for the folks experiencing the problem.
Network speed and packet loss are separate metrics. And the latter is far more relevant to the reported issue.
For me: (I'd suggest folks let it run for at least a few minutes to get a decent sample.)
Code:
My traceroute [v0.86]
ComputerName.local (0.0.0.0) Mon Jun 5 07:37:48 2017
Keys: Help Display mode Restart statistics Order of fields quit
Packets Pings
Host Loss% Snt Last Avg Best Wrst StDev
1. 10.0.0.1 0.0% 2839 1.4 2.0 1.3 6.1 1.2
...
6. ae-1-51.edge2.Newark1.Level3.net 0.0% 2839 80.4 88.8 78.3 480.0 24.8
7. ae-1-51.edge2.Newark1.Level3.net 0.1% 2839 81.8 89.5 78.3 390.7 26.0
8. THE-NEW-YOR.ear3.Newark1.Level3.net 0.0% 2839 83.0 105.4 79.6 400.0 48.4
9. cs20.cs90.v.ewr.nyinternet.net 0.0% 2839 81.9 100.2 80.4 847.4 43.3
10. 199.83.60.138.static.nyinternet.net 0.0% 2839 87.7 95.7 85.4 480.3 25.4
11. mail.messagingengine.com 0.0% 2839 91.3 95.5 85.2 337.0 23.5