According to reports in the Financial Times, Deutsche Post has joined the list of potential bidders that already features TNT and private equity house CVC.
Business secretary Lord Mandelson plans to sell off around 30% of the Royal Mail, but has committed to keeping Royal Mail a majority public owned business.
He has also reiterated that investment from a strategic partner was needed to maintain the six-day-a-week, fixed price "universal postal service".
Speaking in February, Mandelson said: "Our policy will keep Royal Mail in the public sector and this legislation makes that clear.
"The Royal Mail will run out of money to sustain its current universal, six-day service unless its pension fund deficit is solved and its business transformed."
However, the government's search for strategic investment in Royal Mail has not run entirely smoothly with opposition coming from both MPs and trade unions
Last month, it was reported that around 90 Labour backbenchers could oppose plans to part-privatise the operator.
Deutsche Post emerges as 'potential buyer' for Royal Mail
Partial privatisation of the Royal Mail has moved a step closer after Deutsche Post emerged as the latest possible suitor to take part-control of the postal operator.
