Seems like outgoing emails are not following the Retry Intervals (Minutes seperated by commas).

Here's our values:

5, 10, 15, 30, 60, 90, 120, 240, 480, 960, 1440, 2880, 3600, 4320

Here's the logs:

[2022.02.10] 17:18:17.260 [71369192] RSP: 421 bosimpinc03 bizsmtp Server temporarily unavailable. Try again later.

[2022.02.10] 17:18:22.338 [71369192] RSP: 421 bosimpinc03 bizsmtp Server temporarily unavailable. Try again later.

[2022.02.10] 17:23:29.855 [71369192] RSP: 421 bosimpinc03 bizsmtp Server temporarily unavailable. Try again later.

[2022.02.10] 17:23:34.995 [71369192] RSP: 421 bosimpinc03 bizsmtp Server temporarily unavailable. Try again later.

[2022.02.10] 17:23:40.026 [71369192] Delivery for user@local.domain to recipient@remote.domain has bounced. Reason: Remote host said: 601 Attempted to send the message to the following IPs:
[2022.02.10]     xxx.xxx.xxx.xxx, xxx.xxx.xxx.xxx 17:23:40.026 [71369192] DSN email written to 71369318 with status failed to recipient@remote.domain

It should have been in the queue until 72 hours past, since this wasn't a DNS issue, but the recipients server was giving temporary 4xx errors.  The server bosimpinc03 didn't actually show a 6xx error from the logs that I'm seeing.

Edit: We're running the current latest build: