>>> from email.MIMEText import MIMEText
>>> o=MIMEText('hello')
>>> o['Subject']='1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4
5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 '
>>> o.as_string()
'Content-Type: text/plain; charset="us-ascii"\nMIME-Version: 1.0\nContent-Transf
er-Encoding: 7bit\nSubject: 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8
9 1 2 3 4 5 6 7 8\n\t9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 \n\
nhello'
>>>


The '6 7 8\n\t9 1 2 3'  clashes together to 6 7 89 1 2 3
without space between 89 in usual mail readers.
Is this an error and should be :

'6 7 8 \n\t9 1 2 3'


? 

as there is also the space preserved in 
'6 7 8 9 \n\nhello'