Trend of e-mail exchanges over IPv6 @ INFN Milan

Data collected weekly since September 2010.
Spikes are spam, fluctuations are mostly due to waves of spam.
- Can this be the reason for the office/outlook365 differentiated policy for IPv6 ?
But it seems the trend is indeed reversing - bad news.

Here's the list of domains that exchanged more than 10000 messages on IPv6 over 5 years:

Domain	N. of messages	Seen last month ?
`1e100.net`	2598869	Replaced by `google.com`
`infn.it`	1342210	Yes (for the few enabled sites...)
`debian.org`	303073	No
`google.com`	288125	Yes
`garr.it`	105668	Yes
`cern.ch`	91811	No
`desy.de`	49195	Yes
`fnal.gov`	45177	Yes
`fhwn.ac.at`	31928	Yes
`renater.fr`	30961	Yes
`uu.se`	21977	No
`ntua.gr`	15571	Yes
`uib.no`	15322	Yes
`ja.net`	14734	Yes
`linkedin.com`	14451	Yes
`lrz.de`	14410	Yes
`cnr.it`	13814	Yes
`contabo.host`	13449	Yes
`surf.net`	12764	Yes
`ustc.edu.cn`	12411	Yes
`comcast.net`	12342	Yes
`rediris.es`	10308	Yes
`bnl.gov`	10031	Yes