FRA Members ratio in races

[Oracle]

Indeed. Some types of address are treated as suspicious, such as hotmail.
Others like AOL have very low limit rates on how many can be mailed to their users from an outside address.

All recipient services and service providers look at the trustworthiness of the sending source, not just the spam score of the content.( some surprising words can trigger spam filters, words like “ free” or even exclamation marks.

So possibly cockup not conspiracy. The joys of email autoresponders.

It is also why it is far better for organisations to use a trusted auto responser service, rather than mailing from their own domains , although how FRA tackle this I have to confess I have no idea.

Even low end services like mail chimp ( The free service would be adequate for RO mailing) have far better deliverability than own domain, since it is a trusted source, and mail chimp shuts down spammers. These services also automatically throttle delivery over a period

Not all emails are delivered; some end up in spam folders, some are eventually returned by the protocol for various reasons e.g. recipient mailbox is full, some simply disappear. BT, Yahoo, Google have increasingly stringent but apparently inconsistent rules for vetting messages with the result of far too many false positives, i.e. rejections, which are never delivered. Similarly, they apply rules to filter mail servers from which they will accept messages. BT's customer forum has page upon page of complaints about non-delivery. Many messages are excluded for no reason other than another domain on the same server was deemed to have once sent spam. A message can be dumped for having too many recipients, on the basis it implies spam. I spent most of March setting up a stand alone mail server for a club to circumvent such problems due to the number of our emails, which were never delivered.
So forget conspiracy theories, it's likely to be poorly implemented technology, out of the control of the FRA or you and me.