If "Hidden from addressbook" property is set as true, SMTP address of the target object isn't be saved in the Outlook contact item, instead
We have a problem to get a SMTP address for outlook addin.
1. Set "Hidden from addressbook" property to true for certain contact item or sharing group created on Office 365.
Send a mail, adding above mail address in the recipients.
Open the received mail from Outlook using other recipient user then try to save the target object specified in steps 1 as an Outlook contact item.
SMTP address of the target object won't be saved in the Outlook contact item, instead only a part of Legacy ExhangeDN attribute value is saved.