We have major problem about "junk email" . We have an Email Blast software. The system is developed in PHP. We send a thousand emails for visitors promotion. The email contains an image (.jpg, .gif) format. The size of the image is 1200x700. Only the image contains the information about the show and the subject. It seems that every time we send a bulk of email, the email always goes to junk mail of the recipient. We always have this problem. What do you think is the cause of that problem? What are the solutions for this problem?
Questions on Server Fault are expected to relate to server, networking, or related infrastructure administration within the scope defined by the community. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about reopening questions here. If this question can be reworded to fit the rules in the help center, please edit the question.
There are many reasons your mail could be considered junk:
My advice is to not send "email blasts"... Rule of thumb: If the name of a marketing strategy contains the the word "blast", it's not a good strategy.
(In the interest of full disclosure, I work for an anti-spam company)
EDIT: I meant to include this in my answer originally, but forgot...
The best way to answer your question is to examine the logs of whatever software put your software in the Junk mail folder originally. If you don't have access to those logs, perhaps the software was generous (as SpamAssassin is by default, for instance) and added headers to the message that will give you clues as to why it thought the mail was spam.