The problem is most likely experienced only when you are sending to the likes of the big email providers such as Gmail and Hotmail. These providers collect information on the entire system. So if you have sent a email to [email protected]
and then later send the same email to [email protected]
the system knows about the previous send.
Now if your sending a email that is pretty much the same to a@
b@
c@
d@
and so on, at some point its going to be put in the spam box. Spammers will often send out the same email to thousands and this is why this done.
Email Variables
Ideally you want to use variables within your email templates that from customer to customer they slightly change.
For example:
Hi, {Firstname} {Surname}
Thank you for registering at the Job Centre, We hope that you can find your dream job as quickly as possible.
You can edit your profile page here {user-url).
This would have 3 variables that are firstname, surname and user url. This would change your emails so they are not so duplicate and look different from another.
Ensure that your sending using SMTP
Another thing that can help is ensuring that you are sending out the emails using authentication via SMTP. If you are sending your emails with sendmail without login in then the email providers can see this and its very easy to spoof an email address, by using a login server you are confirming that you are indeed sending it from [email protected]
and not a email address made up.
Another possibility is that people are flagging your emails are spam, I believe that Google and Hotmail for example collect this data and can consider emails spam based on user feedback, though if your emails are legit, then this shouldn't be a problem.