Hints for Amazon Simple Email Service (SES):

• avoid a misinterpretation like _amazonses.example.com.example.com in a DNS record name.
• end a DKIM value with a dot to tell that the domain name is complete.
• just close and open in order to successfully verify, or generate / verify again (having the same DKIM values).
• DMARC does work; a dmarc=fail may be caused by SPF or DKIM setup.
• Check for no more than ten DNS lookups.
• SES works with the SRS authorization technique, which is flexible.
• a file with login details is an option; for me a database table works with an input form.
• the spam score may be a problem (greenlist / whitelist).
• if using ‘forged reply to’, a spam score is raised, mentioning: FREEMAIL_FORGED_REPLYTO.
• maybe keep the sender address and reply address identical not to end up as spam.

SES with the Simple Mail Transfer Protocol (SMTP):

• DNS settings and credentials under SMTP settings.
• firewall CSF must have SMTP_BLOCK disabled for the SMTP proces.

SES in the Software Development Kit (SDK or devkit):

• DNS settings and IAM user credentials.
• PHP manual: The ‘use’ keyword must be declared in the outermost scope of a file (the global scope) or inside namespace declarations. This is because the importing is done at compile time and not at runtime, so it cannot be block scoped.
• my working PHP code: Coding for improved SDK Usage