In case you aren't aware, we have a subscription system for content posted to the site. By default we automatically subscribe members to job postings. Any member can subscribe to an assortment of content by type, author, or a specific content item. When content is added or updated, an email is sent out to the member's account email address.
A small number of members are using Yahoo email addresses and those subscriptions are being rejected. So in those cases, you aren't receiving any updates about your subscriptions, primarily the most recent job opening posted to the site.
While the original bounces were only "temporarily deferred", Yahoo is now blocking these emails immediately. I need to get us "whitelisted" with Yahoo so the emails can go through unabated. I don't administer our mail servers so I need to contact our ISP.
In the mean time I'm going to have to remove subscriptions for members using Yahoo.com email addresses. Once we get whitelisted those subscriptions will be turned back on.
Another solution might be for those members to drop Yahoo.com in favor of a better email provider. We send out approximately 4-6 emails a month to 60 subscribers, only 10 of these go to Yahoo.com. Yahoo apparently considers this spammy behavior.