Python Email Bot Fixes

I have a communication bot written in Python that handles automated emails for multiple accounting firms. Overall the codebase is solid, but some messages never reach their destination or end up in spam. I need a Python specialist to review the existing modules, pinpoint why delivery fails, and implement a clean, minimal fix without breaking current functionality.

Here is what I expect from you:
• Read through the current source (Python 3, standard smtplib with a fallback to an SMTP relay).
• Trace the flow that assembles and dispatches the automated mails, including error handling and any retry logic.
• Identify and resolve the root cause of the delivery issue—whether that is authentication, header construction, rate limiting, or something else buried in the logic.
• Commit the corrected code plus a concise note explaining the change so my in-house team can follow the rationale.

You will receive full access to the repo in a private Git branch as soon as we agree on the engagement. A successful hand-off is a pull request that passes our test suite and proves, via a simple before/after log, that every scheduled message reaches the intended inbox.

If you are comfortable with mail servers, SPF/DKIM tweaks, and neat, readable Python, let’s get this sorted quickly.