Improving email deliverability for solicited business proposals to corporations requires a holistic strategy focusing on sender reputation, authentication, list hygiene, engagement, technical compliance, and adaptation to the recipient's email ecosystem. Building and maintaining a positive sender reputation through consistent sending of valuable content, low complaint rates, and proper authentication (SPF, DKIM, DMARC) is crucial. List hygiene is vital; regularly clean lists and validate email addresses to minimize bounces. Enhance engagement by personalizing and segmenting emails, avoiding spam trigger words, and ensuring proper formatting. Adhere to SMTP standards (RFC 5321) and consider joining provider support programs (e.g., Microsoft). When acquiring contacts, be mindful of the collection method. Tailor the initial communication to be non-spammy, and consider the recipient's email provider (e.g., Gmail, Outlook). Gradually warm up IP addresses. Monitor for blocklisting, use dedicated IPs when appropriate, and always obtain explicit consent.