Hi Andy,
Are you sure it’s Postfix doing it? 
I don’t want to doubt you but it does seem odd, so I am wondering if there some 
other piece of the puzzle we may be missing.

Can you tell us a little bit more about your setup as far as mail relaying 
goes? 
Is there another mail relay involved? Is a relay host set in postfix? 
Did you change any of the defaults in PacketFence regarding mail relaying and 
notifications? Check your conf/pf.conf if in doubt.

Finally, does this also happen when sending emails without involving 
PacketFence? 
E.g. does it also affect any email sent using “mail”, as in 

# echo "This is a test of a very long line for which I am the very model of a 
modern MTA. PS. Sendmail is dead." | mail -s test [email protected]

Regards,
--
Louis Munro
[email protected]  ::  www.inverse.ca 
+1.514.447.4918 x125  :: +1 (866) 353-6153 x125
Inverse inc. :: Leaders behind SOGo (www.sogo.nu) and PacketFence 
(www.packetfence.org)

> On Nov 19, 2015, at 8:00 , Andy A <[email protected]> wrote:
> 
> Hello. 
> 
> We are running PF 5.2 in in-line mode on Centos 6.x
> We have postfix running locally with opendkim, opendmarc. All the packetfence 
> emails are sent via the local MTA (postfix)
> 
> The mails are being delivered and are signed as they have DKIM signature, but 
> the body hash fails. DNS TXT records for dmarc, dkim and spf are all valid 
> and present. We have figured out what the issue is. Postfix is chopping 
> certain lines of the messages  after a total of 74 characters. This is quite 
> strange as the line length limit for Postfix is 998 characters and SMTP 
> protocol line length limit is 1000 characters. But, what's even more puzzling 
> is that the messages which are being sent out as text/plain are also being 
> subjected to this chopping. 
> 
> Thus, the messages which have lines longer than 74 characters get chopped and 
> split into two lines after DKIM signature is applied to the mail message. 
> This results in incorrect body hash on the verifier's end. I have tested this 
> with two different messages stated below.  I used the 
> emails-guest_admin_pregistration.txt.tt template for this. Can anyone suggest 
> what's going on and how can this be resolved?
> 
> Following is the original template messages which fails the DKIM verification 
> at the verifier's end. As you can see, the lines have been chopped off and a 
> '=' has been added towards the end of the line where the lines have been 
> longer than 74 characters.
> 
> Hi  ,
> 
> An account has been created for you to access our network.
> 
> Once you will be on-site, authenticate using the following credentials to=
>  our captive portal:
> 
> Username: email.verify
> Password: password
> 
> This username and password will be valid starting 2015-11-18. Registratio=
> n must happen before 2015-11-19. Once authenticated the access will be va=
> lid for 1 hour.
> 
> Please ignore this request if you have not requested network access.
> --
> This is a post only E-mail, please do not reply.
> 
> 
> 
> Following is the message which passes the DKIM verification at the verifier's 
> end. I modified the template message so that no lines are longer than 74 
> characters.
> 
> Hi  ,
> 
> An account has been created for you to access our network.
> 
> Username: email.verify
> Password: password
> 
> Please ignore this request if you have not requested network access.
> --
> This is a post only E-mail, please do not reply
> ------------------------------------------------------------------------------
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