Here is the setup
1. Sender is using Office 365
2. Sender workplace does not have fixed IP.
3. Sender's workforce is mobile. Could work from many different locations including wifi hotspot, 3G/4G, client wifi, etc
Recipient mail server is refusing email from sender. Office 365 (sender mail server) sent an NDR message to the sender - see below
Question 1: Is the recipient mail server reacting to where the emails come from (Office 365 server) or where the emails were created (the IP of where the Outlook was when the email was created)?
Question 2: Is there a solution to this issue? The sender's workplace ISP does not offer fixed IP. The "Outlook's ISP" can change on a daily basis. So is there a solution to this issue?
Your message to email@example.com couldn't be delivered.
A security check at recipient.com failed due to misconfigured settings at sender.com.
Action Required: Misconfigured PTR record
How to Fix It
The recipient's email server at recipient.com performed a security check against your message and the check failed. To fix this, forward this non-delivery report (NDR) to your email admin.
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More Info for Email Admins
Status code: 550 5.7.363
It appears that the recipient's email server at recipient.com performed a reverse DNS (rDNS) lookup security check to verify that the IP address the message is coming from is associated with the sending domain, and the lookup failed. It appears that the pointer (PTR) record for sender.com isn't set up correctly.
Set up or fix your domain's PTR record - If you're the admin for sender.com, work with your DNS hosting provider (your domain registrar, Web hosting provider, or ISP) to correctly set up a PTR record for your domain. If you're using Office 365 to manage your DNS records note that PTR record creation and management isn't supported in Office 365, so you'll have to change your DNS management to a DNS host outside Office 365. Refer to this article for more information and instructions: Change how DNS records are managed with Office 365.
Unfortunately, Office 365 Support can't help you fix these kinds of externally reported errors because Office 365 doesn't support PTR record management.
Original Message Details
Created Date: 12/08/2016 3:54:42 AM
Sender Address: firstname.lastname@example.org
Recipient Address: email@example.com
Subject: test email
Reported error: 550 5.7.363 Remote server returned sender verification failed -> 550 Verification failed for <firstname.lastname@example.org>;No Such User Here;Sender verify failed
DSN generated by: HK2PR04MB1700.apcprd04.prod.outlook.com
Remote server: ctp8kvm5.webhosting.openconnect.com.au