Secure mail server iintergration

Any good all in one dovecote exim4/postfix clamav spamassassin graylist dkim etc mail integration suggestion with nextcloud?

I’m under debian stretch and I found mail in a box but just realised it’s supposed to be for ubuntu and I don’t really trust it since it’s Us based and may be less secure than debian.

I wanted to use iRedMail but it looks like it’s not quire popular and is also chinese.

Any thoughts?