Ian,
This week I found out that the reminder emails I have going out are
appearing in some member's email inboxes as spam.
Is there anything I can do from my end to help whitelist these
messages?
The one thing you can do, if you are the one creating the events, is to include a reasonable amount of specific information in the event description. Content-sensitive spam filters are typically more likely to pass a message that has more unique content.
But generally speaking, no, whitelisting is something the affected members have to take care of themselves.
In some email services it is sufficient for the member to mark those messages as "not spam" a few times and the filter will learn. Others offer that promise but don't learn - or not very quickly.
In some email services putting the sender address in the user's address book will "whitelist" that sender (for a group's event notices, that would be the group's posting address).
In some email services you can create a filter that recognizes, say, the group's subject tag and moves all messages with that tag in the subject to the user's inbox (overriding the spam filter).
Shal
Shal Farley