Description of problem:

I sent an email regarding a change to an annotation in a Jenkinsfile, instructing them to use a specific branch of the library.  The email I created had the information correct, but the actual email that was sent—and that was placed in my "Sent Items" folder—contained spaces that would have broken the code.

Version-Release number of selected component (if applicable):

evolution-3.26.4-1.fc27.x86_64

How reproducible:

I've been able to reproduce it several times.

Steps to Reproduce:
1. Compose a new message and select the body of the message.
2. Select "Preformatted" from the "Paragraph Style" menu.
3. Tap the "Increase Indent" button once.
4. Paste (specifically paste, with C-v; not type) the following text:
    @Library('library@master')
5. Select the text "master" from above and delete it by hitting backspace.
6. Paste (again, specifically paste, with C-v) the following text:
    some-branch

Actual results:

Even though the editor window will show text looking like the following:

    @Library('library@some-branch')

The actual email that is sent will look like:

    @Library(    'library@some-branch    ')

(Note I have not specifically counted the added spaces or looked closely at the actual byte-by-byte contents of the sent message.)

Expected results:

What I see in the editor window prior to sending the email should be exactly what gets sent.

Additional info:

As far as I can tell, reproducing this bug requires using "Preformatted" paragraph style, one level of "Increase Indent", and using c&p with the C-v keystroke.  In particular, I was not able to reproduce this by just typing the text directly.  I only had time to perform 3 tests after observing the bug, however, and it may be worthwhile to try varying some of the bits to see if a more minimal set of instructions can reproduce it.