Blesta Email Goes to spam sometime on yahoo and gmail.
The 'List-Unsubscribe' header is missing. Including this header allows recipients to easily unsubscribe from your mailing list without having to search for an unsubscribe link in the body of the message. Google and Yahoo made a one-click unsubscribe a requirement. Consider adding the 'List-Unsubscribe' header to enhance user experience and comply with the best email practices. Read more:

Google subscription requirements and guidelines
https://apps.google.com/supportwidget/articlehome?hl=en&article_url=https%3A%2F%2Fsupport.google.com%2Fa%2Fanswer%2F81126%3Fhl%3Den&assistant_id=generic-unu&product_context=81126&product_name=UnuFlow&trigger_context=a&fragment=subscriptions%26zippy%3D%2Crequirements-for-sending-or-more-messages-per-day
Yahoo one-click unsubscribe
https://senders.yahooinc.com/subhub/