"In case you were not watching TV today, the Western Cape High Court has suspended your unconditional cessation of membership of PDL [Patricia de Lille]," the letter said.
"I am told that right now your lawyers are reporting to your white masters who are so angry, and they are discussing an appeal and to [bring] forward another vote of no confidence in PDL."
Nkohla told Maimane there were plans to have him assassinated.
". you are [the] only known enemy to me . I am aware Mmusi, as your DA people have been following me every day. They even [stole] my carpet with an aim of bugging it to listen [to] every conversation I have at my place."
In the letter, Nkohla warned Maimane the DA would get rid of him after the general elections next year.
"Mmusi, we have warned you but you decided to undermine us and listen to white views because they make sense to you," the letter said.
"You are next . after 2019 general elections. Whites in the DA have decided to claim their party back from the hands of black leaders because it was Helen [Zille's] project, they don't believe in that. They have started by having Natasha [Mazzone] as an imposed deputy chairperson of the [federal executive] and spokesperson."
Maimane's spokeswoman, Portia Adams, said: "I'm sorry but I'm not going to dignify this with a response."