I've built a system for a client to send html based emails. I'm having a problem that any external email address is rejected by the Send Email function. Looking at the logs I can see the following: 

Quote

 

nested exception is:
com.sun.mail.smtp.SMTPAddressFailedException: 550 5.7.64 TenantAttribution; Relay Access Denied [DB5EUR03FT020.eop-EUR03.prod.protection.outlook.com]

at com.sun.mail.smtp.SMTPTransport.rcptTo(SMTPTransport.java:1949)
at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:1195)
at com.prosc.emailplugin.EmailerModel._sendMessage(EmailerModel.java:645)
at com.prosc.emailplugin.EmailerModel.send(EmailerModel.java:610)
... 7 more
Caused by: com.sun.mail.smtp.SMTPAddressFailedException: 550 5.7.64 TenantAttribution; Relay Access Denied [DB5EUR03FT020.eop-EUR03.prod.protection.outlook.com]

 

I've spoken to the client's IT support who manage their email server and checked all the details used. It appears this is caused by javamail, but we're not sure how to get around this issue. Has anyone had a similar issue, and how did they get around it? 

The 'Relay Access Denied' message is generated by outlook.com. Are you authenticating when you send an email? This article https://www.lifewire.com/what-are-the-outlook-com-smtp-server-settings-1170671 describes the smtp settings needed.

Is the mailbox you're sending as allowed to send email to external addresses?