Rediff.com’s revenues have declined from ~$12M annually in 2010 to under $2M by 2020. Rediffmail usage is a fraction of its peak.
If you forget your password, you can use the "Forgot Password" tool. If the hint answer is also forgotten, users can reach out to customer care to have a reset link sent to an alternate email. rediffmail
However, below is a comprehensive styled document regarding Rediffmail. This document covers its history, technical architecture, business impact, and evolution in the Indian market. You can use this as a complete reference paper. Rediff
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