R1:ee814923a22e

Improve Amazon SES code error handling behavior

Summary:
Fixes T10728. Fixes T10476. SES uses third-party code with unique, creative ideas about error handling.

- Make the error handling behavior more correct, so it doesn't try to use undefined variables.
- Simplify the error handling behavior (throw exceptions sooner, remove redundant code).
- Explicitly test for `-smtp` misconfigurations. These can arise if you read the wrong column out of the table in the AWS docs, as in T10728.
- Explicitly…