What is the 'from address' on messages from your list, so I can whitelist it?
Someone asking this question is typically talking about the visible From: header displayed in each recipient's email program. For the mailing lists we host, that can be whatever address you've requested. That is the address which is typically checked by email clients (Outlook, Outlook Express, Thunderbird, etc.) and if a match is found in the contact list, the message is not filtered (i.e. "whitelisted").
However, to be technically accurate, there are TWO from addresses on every message. In addition to the visible From: mentioned above, each message also has a "Return-Path" aka envelope from_ address, which identifies the actual server sending the message.
For a person-to-person single email message, those two addresses are typically the same. However for mailings sent to mailing lists (e.g. those we host), the addresses do not agree. The Return Path address is unique for every message. That is because we use VERP ("Variable Envelope Return Path") to manage bounces.
For example, a mailing we send for Acme Widgets might have a visible header like this:
From: Acme Widgets News <email@example.com)
But the Return Path for a message sent to subscriber Wendy Williams would be:
... where "acmewidgets" is different for each list, and "wendywilliams=gmail.com" changes for every recipient.
[Note this page does apply to our discussion mailing lists, which do not use VERP.]