Gmail uses lot of criteria to determine if an incoming email is good one or spam. Those criteria include –
If it is auto generated by so as to conceal the sender email.
If it contains words like cialis, cheap rolex watches, viagra etc, repeated at many places.
If the email contains many links to different websites
If you mark some email as spam, etc.
See more of such criteria here. But more often than not, some of the legal emails unfortunately qualify as spam and end up in spam box. Many of my patient queries end up there, and I make it a habit to check it once a week so that I do not miss any of the emails.
It happens so that, people who subscribe to my Ayurveda blog receive an email confirmation link. But most of the times, this email also goes into spam box and they do not confirm the email subscription and hence do not receive my new health articles into their inbox.
If you subscribed to my Ayurveda blog and have not been receiving any of new articles, please check your spam box once, and please confirm your subscription.
I also have an email account in sify, which sometimes sends password reset email to spam!