Update Amazon SES Header Cleaning Function

As per AWS Documentation, Amazon SES accepts any email headers that
follow RFC 822, so the cleaning function isn't necessary anymore.

http://docs.aws.amazon.com/ses/latest/DeveloperGuide/header-fields.html
Fix early return when sending via Amazon SES

"return 1" is called too early when sending via Amazon SES, which
results in no logging if LOG{mailings} is enabled
Enable retrieval of result returned by SES

Allows a developer to retrieve the Message ID that Amazon SES gives upon
successful sending of email
Merge pull request #435 from Yunheng/master

Issues when sending via Amazon SES