int c;
int p = 0;
smtp_printf("334 %s\r\n", b64encode(challenge, challen));
-while ((c = receive_getc()) != '\n' && c != EOF)
+while ((c = receive_getc(GETC_BUFFER_UNLIMITED)) != '\n' && c != EOF)
{
if (p >= big_buffer_size - 1) return BAD64;
big_buffer[p++] = c;