You can adjust your Email Notifications/Advanced Email settings by hovering your mouse over your name (top right of your browser window).
NOTE: this adjusts whether or not you get emails at all -- not whether you're subscribed to this or that Group, or changing email settings for a particular Group. (For information on adjusting your email settings for a Group, click here.)
When you do this, a drop down will allow you to go to Settings, then Notifications:
A more advanced set of options will appear, allowing you to fine-tune your email notifications regarding what activities send you email at all.
To put a hold on all mail from Shambhala Network, change the boxes from "yes" to "no."
Once you return from your vacation, remember to change these back. Otherwise, you will not receive any email notification from the Shambhala Network. (HINT: it's good to add a calendar reminder to tell you to do this.)
This only turns off email for the Shambhala Network. If you're wanting to put your emails from the older shambhala.org email lists on hold (sangha-announce, sangha-talk, etc. -- scheduled to be discontinued in 2012), you'll need to read this helpful article