There are a number of reasons your email could be flagged. It could be because you're using an unprofessional email address, you're sending too many emails, or you're not personalizing your messages enough. It could also be that your emails are going to spam folders because they contain too many links or keywords that trigger spam filters. To avoid being flagged, make sure you're using a professional email address, tailoring your messages to each recipient, and keeping your links and keywords to a minimum.