Sending a one-sentence email that is just a prelude to a large graphic that makes up 90% of the message is not a good idea. Avoid using graphics altogether when emailing more than one person. Stick to text, and if you want to share something visual, use a link (preferably from your own domain, don't use a link shortener).
The title of the message should be specific and clear. Vague phrases like "You chinese overseas australia database just won!" or "Buy now!" will only get you in trouble. Write the message first, and then, based on the content, come up with a title that is not confusing or unclear.
For example, if you want to send your subscribers an email about new products in your online store, a good and clear subject line should sound something like this: "Check out the new products you'll love."
This subject line is still marketing and engaging, but the recipient knows what to expect. It's a much better solution than "Buy now! Hot deals!"
Linguistic correctness
Finally, your emails should be linguistically and grammatically correct. Poor Polish and typos are another serious red flag for anti-spam algorithms. Check every message before sending (ideally twice). You can use many available grammar checkers. Some of them (e.g. Language Tools) are available for free.
Make sure your language is easy for your audience to understand (don't overdo it with fancy or eloquent terms) and free of typos and other errors.