I use Google's SMTP server for outbound email. As we all know, when sending using another providers SMTP, the recipient sees "FROM: ??gmail.com [on behalf of ??tampabay.rr.com]"

My question is, how do ISP's spam/junkmail filters handle this situation? Do they filter on gmail.com or tampabay.rr.com? Is it provider-specific?

My concern is that several people/businesses that I correspond with had to allow my tampabay.rr.com address through to their Inbox. Am I going to have to notifiy these people to also allow gmail.com?