It happens with most of the users, when they continuous trying to send the mail, but their mails are bounce back or rejected and at the same time user receive an error message which saying that “message rejected”. Basically it means your message is not successfully delivered to any user. This happens just because of your account characteristics and content of your message that’s why it marked as spam. If you feel the same scenario then immediately follow the post which I describe below, which helps you to solve this problem.
1) The problem is related to your Cc or Bcc when you send bulk of mail. That’s why your Gmail account is marked as spam. To get rid of this problem I recommend you to use Google group to send out the message to a large number of people.
2) If you found that your message is rejected again and again, then change your web browser. Might be possible the issue is related with your web browser.
3) Due to internet issue it happens, so immediately contact to your internet service provider and ask them to fix this issue.
4) Make sure, if you are using any kind of POP/IMAP then immediately sign out and sign in again. Hope it works.