If you're using Gnus to read mail and have properly insinuated it (see Insinuation), Patcher offers different Gnus-like ways to answer mails and adapt them to Patcher. All the functions below are available from both the Gnus Summary and Article buffers.
Compose a followup to an article, and adapt it to Patcher. This function is bound to C-c C-p f.
Idem, but also cite the original article. This function is bound to C-c C-p F.