In-House Year-End Tax Receipting via email

My organization is looking into emailing our 2025 tax receipts in early 2026. We have done a lot of researching and find it can be done by creating a PDF and mailing the receipts but we haven't figured out how to email them to our supporters. Normally we outsource the project but this year we are hoping to complete the task in-house. Any tips on this would be appreciated.