code: public com.squareup.okhttp.Call deleteCharactersCharacterIdMailMailIdAsync(Integer characterId, Integer mailId,
              String datasource, String token, final ApiCallback<Void> callback) throws ApiException {
  
          com.squareup.okhttp.Call call = deleteCharactersCharacterIdMailMailIdValidateBeforeCall(characterId, mailId,
                  datasource, token, callback);
          apiClient.executeAsync(call, callback);
          return call;
      }
docs: Delete a mail (asynchronously) Delete a mail --- SSO Scope:
  esi-mail.organize_mail.v1
  
  @param characterId
  An EVE character ID (required)
  @param mailId
  An EVE mail ID (required)
  @param datasource
  The server name you would like data from (optional, default to
  tranquility)
  @param token
  Access token to use if unable to set a header (optional)
  @param callback
  The callback to be executed when the API call finishes
  @return The request call
  @throws ApiException
  If fail to process the API call, e.g. serializing the request
  body object