Subject: test email
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="----=_Part_31262_376962461.1389046146932"
X-SFDC-ORGTYPE: FREE
X-SFDC-LK: 00D50000000IQwR
X-SFDC-User: 00550000001Zf61
X-Sender: postmaster@salesforce.com
X-mail_abuse_inquiries: http://www.salesforce.com/company/abuse.jsp
X-SFDC-TLS-NoRelay: 1
X-SFDC-EmailCategory: emailAuthorEmail
X-SFDC-EntityId: 000000000000000
X-SFDC-Binding: 1WrIRBV94myi25uC
X-pstn-neptune: 0/0/0.00/0
X-pstn-levels: (S:49.31071/99.90000 CV:99.9000 FC:95.5390 LC:95.5390 R:95.9108 P:95.9108 M:97.0282 C:98.6951 )
X-pstn-dkim: 0 skipped:not-enabled
X-pstn-cm-addresses: from <wbamann@salesforce.com> (approved)
X-pstn-settings: 3 (1.0000:0.0005) s cv gt4 gt3 GT2 gt1 p
X-pstn-addresses: from <wbamann@salesforce.com> forward (org good) [db-null]
X-pstn-nxpr: disp=neutral, envrcpt=wbamann@salesforce.com
X-pstn-nxp: bodyHash=fc046c0b5e85cebaf6cfb21b69bd44573fc1d653,
headerHash=479949543731a27d88943ececf83136227a00a56, keyName=4,
rcptHash=d2bdf7edb11a749779317b57aa4594a2c9712fa7,
sourceip=204.14.232.79, version=1
------=_Part_31262_376962461.1389046146932
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
test email
THIS IS A TEST
_____________________________________________________________________
Powered by salesforce.com
http://www.salesforce.com/
------=_Part_31262_376962461.1389046146932
Content-Type: text/html; charset=UTF-8
You can see the Fields that will identify the type of organization sent the Email as well as the ID and the User.
X-SFDC-ORGTYPE: FREE X-SFDC-LK: 00D50000000IQwR X-SFDC-User: 00550000001Zf61h
NOTE The field X-SFDC-ORGTYPE will only display from Emails sent out of "Free' or "Trial" Orgs. This will not display when sent from
any other environment.
Best Answer
You can find the details in below-mentioned links.
Source: https://help.salesforce.com/articleView?id=000205334&type=1
Source: https://help.salesforce.com/articleView?id=000188046&type=1