When emailing invoices to the clients from ArchiOffice (or EngineerOffice), the users get the following error message from the recipient email servers:
451 4.4.4 Temporary server error. Please try again later ATTR5
This can happen if your SMTP server IP address has been blacklisted or graylisted by the recipient Office 365 server or has a configuration setting that the recipient Office 365 server is rejecting. It can also happen if the Office 365 server is trying to throttle your connecting IP address. You may have sent bulk emails to the Office 365 tenants, including the ones who have not whitelisted your IP address in their connector or connection filtering. In this case, Microsoft starts to throttle your IP and generate the temporary error. It does this to stop spam emails for their customers.
To resolve this issue, you can try the following solutions:
- Ask the mailbox owner or administrator of the recipient email address to open a ticket with Microsoft Support. They can do that using the Support link in the Office 365 portal.
- Use the Inbound SMTP Email and the Outbound SMTP Email options from the Office 365 tab on the Microsoft Remote Connectivity Analyzer site to check connectivity of your SMTP server with the recipient Office 365 server.
- Send a test email from the mail server machine that is failing, using the below PowerShell script:
Send-MailMessage –To firstname.lastname@example.org –From email@example.com –Subject "Test Email" –Body "Testing O365 Service" -SmtpServer mx_of_domain.mail.protection.outlook.com -Port 25
where you need to replace firstname.lastname@example.org with the email address of the recipient, email@example.com with your own email address and mx_of_domain.mail.protection.outlook.com with the MX server record of the recipient. You can find their MX record from mxtoolbox.com. If it works, then your SMTP mail server is the issue. If not, then your IP address may be blacklisted.
- Use MultiRBL and Talos Intelligence to ascertain that your external IP address is not on any blacklist. If that is the case, you need to take it up with your ISP or check your connection IP health at sender.office.com.
- Your company can directly open a ticket with MS Office 365 to troubleshoot the issue.