For anybody still looking into this thread - I found some helpful tips at https://docs.aws.amazon.com/ses/latest/DeveloperGuide/Welcome.html
Changing the port to 587 and using explicit tls seems to have resolved the issue.
We also started to experience similar behavior. We were using port 465 though. This was happening to about 10% of outcoming mails.
We implemented a retry mechanism. If sending fails it will be tried again in 1 minute. This solved this issue (for now).
I've also tried to switch to port 587 - but the outcome is the same as on 465.
Hello did you ever get to the bottom of this? I'm suffering through the same issue here
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