William J. Mills, Murray S. Kucherawy. The Require-Recipient-Valid-Since Header Field and SMTP Service Extension. RFC, 7293:1-24, July 2014. [doi]
@article{rfc7293,
title = {The Require-Recipient-Valid-Since Header Field and SMTP Service Extension},
author = {William J. Mills and Murray S. Kucherawy},
year = {2014},
month = {July},
doi = {10.17487/RFC7293},
url = {https://doi.org/10.17487/RFC7293},
researchr = {https://researchr.org/publication/rfc7293},
cites = {0},
citedby = {0},
journal = {RFC},
volume = {7293},
pages = {1-24},
}