Unnecessary spaces are automatically inserted to posts

Hello. This is the first time for me to create a new topic.

In posts that are created through Postie, there are spaces inserted in text, which mails I sent to Postie do not contain.

For example,
While a part of my mail sent is below,
<script type="text/javascript">~~~</script>

the post actually posted was
<script type="text/javascript">~~~</scrip t>

As you can see, extra space is inserted in “</script>.”

For another instance,
While a part of my mail sent is below,
男のゴツゴツとした手

the post actually posted was
男の ゴツゴツとした手が

In this case, space is inserted after “男の.”

Since spaces are inserted in the middle of html, posts are not shown right on the website.

Does anyone know why this is happening?
Thank you.

My settings are as below.
Text Type: Plain
Text Fallback: Yes
Allow HTML In Mail Subject: No
Allow HTML In Mail Body: No
(I changed these settings and tried again, but the problem was not solved.)