Can i ask what is the most important think to setup an email to not go into SPAM?

Can i ask what is the most important think to setup an email to not go into SPAM?

Hi,
I'M trying Zoho mail and is lovely !

Tested and sent emails not goes into user spam.
I have a VPS managed by a WebPanel but maybe they not configure well the email and they goes into SPAM.

I don't know if i can ask here, as i see you are lovely and professional on delivery of the email,
if the server IP is not blocklisted

i know for the email is important set correctly SPF, DIKIM .. but for example i have see in my VPS email i have setup SPF and is passed into header so works but gmail deliver into SPAM my emails. I was thinking was because i had not DKIM but i have see also other email (not mine) who arrive in Gmail inbox and has DKIM not valid.

I'm curious.. is so hard configure well emails for work for example in a VPS?

Good service yours.. i think maybe i want share with other people - and is a way to say thank you for exist and do what you do.
Acctualy I'm not into business so i can't have big expence but i will look into your premium plan. Thanks also for make Zoho accessibile to everyone - also to people who can't pay a lot.. it's a good idea i think maybe one day this user can grow the desire to grow up and upgrade :)

Free world is the best thinks