Forum Discussion
Invite external user - error 'Primary SMTP address is an invalid value'
I'm using Entra Id to invite external users to my domain.
Their email is of form: mailto:email address removed for privacy reasons
Sending the invite generates the error:
There is no error if I send an invitation to the same domain without the '+' sign, so I assume this is causing an issue with Entra Id.
Is there a workaround for this?
You’ve hit one of the quirks of Entra ID B2B invitations. :D
The error “The Primary SMTP Address is an invalid value” appears because Microsoft Entra ID validates the primary SMTP address against RFC rules and does not accept “plus addressing” (email address removed for privacy reasons) when it is used as the invite target. Many email systems accept plus-tagging, but Entra’s invite API rejects it.Once the user is provisioned, they can still receive mail at their plus-tag address, but the identity in Entra is always anchored to the base SMTP address. there’s no way to make Entra ID accept the “+” form directly. You need to invite the plain SMTP address of the user, and the email system on their side will handle delivery of plus-addressed mail.
2 Replies
You’ve hit one of the quirks of Entra ID B2B invitations. :D
The error “The Primary SMTP Address is an invalid value” appears because Microsoft Entra ID validates the primary SMTP address against RFC rules and does not accept “plus addressing” (email address removed for privacy reasons) when it is used as the invite target. Many email systems accept plus-tagging, but Entra’s invite API rejects it.Once the user is provisioned, they can still receive mail at their plus-tag address, but the identity in Entra is always anchored to the base SMTP address. there’s no way to make Entra ID accept the “+” form directly. You need to invite the plain SMTP address of the user, and the email system on their side will handle delivery of plus-addressed mail.
Thanks for confirming the cause.
Although plus-addressing/sub-addressing/filtering is not part of RFC822 (which Enterprise ID supports) but is part of RFC5233, I thought that '+' was always a valid character for the local part of an address.
