People are overestimating the importance of the message body in spam classification. The stuff that appears in your spam label on gmail is what google considered marginal, almost ham. The vast, vast majority of what they think is spam is rejected with temporary failure codes at SMTP time and never gets delivered with any label. IP reputation and other related metadata features are the key features in spam classification, and repeatedly sending different messages is not a valid test of whether the body looks spammy or not.