Please help to correct my understanding.
When an email fall to a SPAM folder, what my understanding is either SPF or DKIM or DMARC not set correct or SMTP's IP address had been blacklisted.
When I receive newsletter or welcome email which fall into my SPAM folder. I always curious and try to check their header using mxtoolbox's Header Analyzed.
Sometimes I do see either one I mention above having an issue, but some time I do saw everything set nicely
Ok Icon SPF Alignment
Ok Icon SPF Authenticated
Ok Icon DKIM Alignment
Ok Icon DKIM Authenticated
IP no Blacklisted.
Yet, it falls into my SPAM box.
Usually what reason the email will fall into SPAM? Is it because of my email service provider more strict in term of receiving email?
Reason I want to understand more, so that I can optimize my email, ensure the deliverability high.