We share the frustration with the failure rate of emails within a blast.
When these failures happen the system is fully aware of it and suggests that the admin attempt a re-send to the failed addressees. The re-send typically corrects the failure.
Occasional failures are endemic within communications systems and any well designed system handles them automatically as an essential feature of its design.
In this case, Wild Apricot :
1. knows exactly which failures have occurred, and
2. knows exactly how to correct them - do a re-send.
It's unfortunate that the WA designers chose to off-load the responsibility for correcting this system failure onto the admin.
In my communications with the WA help desk, I'm told that this results from the way WA sends blast emails and, unfortunately, there is no correction scheduled.

A recent email blast to 1491 members had 22 failures, including errors- 450, 451 (greylisted; try again later), 452, 551 (blacklisted) and 554. After using 4 Resend to Failed options over two days, followed by 2 direct resends, I had 100% delivery. WA should handle these various ISP throttling methods without our manual intervention.

We've had lots of earthlink emails "Undeliverable" recently too! And, we don't have the capacity to monitor email rejections more than occasionally! Please please work with earthlink to resolve this issue!

It would also be beneficial to have the system instead try a secondary address instead of the primary, automatically.

Retrying 421 return codes for a number of days before giving up has been part of mail servers for years. Surprised to discover WildApricot tags these codes as failures and we need to watch logs and manually do retries. At least there is a button to make it simple.

Removed the phone, no worries.
Just be careful next time when publishing something on public forum like our Wishlist.

Geez, didn't think my email would turn into this suggestion... including my phone number and typo's ;-)

Changed the title of the proposal in order to better reflect the idea.