[exim] Additional line in body when submitting?

I have some instances, which generates mail from stdin
(ie something like "echo bla|mail root")
and recently I found that there exists additional empty line in such
emails, ie instead of
--8<---------------cut here---------------start------------->8---
bla
--8<---------------cut here---------------end--------------->8---

I have

--8<---------------cut here---------------start------------->8---
bla

--8<---------------cut here---------------end--------------->8---

I am rather confusing with it. Is this intentional?
KJ

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