Unfortunately, there's no easy way for you to ensure your emails don't hit the Promotions tab. It's also unclear how Gmail decides whether an email is "promotional" or not.
Below is how to "teach" a gmail account to treat your emails as primary.
This can be done by clicking on the email (without opening it) & dragging it to the "primary tab". You will then see a message that says:
"The conversation has been moved to "primary". Undo
Do this for future messages from "email address x"?Yes"
If you click yes, all future emails from that address will go to the primary tab.
This will certainly work for each individual who does it, I.e.. Each person who does it, their gmail account will always send your emails to the primary tab.
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