Any and all emails received from GW2 support fail to pass authentication causing Hotmail to flag the emails as suspicious. I do not enjoy this as it means there is no easy way to distinguish between legit and illegitimate emails pretending to be from GW2.
I check the Source of the emails and have already made a support case regarding this, if it can’t be changed/fixed then I suggest using plain text URL’s instead of hyperlinks in your emails.