That's weird. Does it happen for *any* recipient name or just for some? What is the exact string that you pass to Recipients.Add?
Since you can create a valid recipient using MAPIUtils.CreateRecipient, you can simply copy the resolved properties to the Recipient returned by Recipients.Add:

Recip1.Fields(PR_ENTRYID) = Recip2..Fields(PR_ENTRYID)
etc for the PR_ADDRTYPE, PR_DISPLAY_NAME, PR_EMAIL_ADDRESS properties.

Another workaround is to add the recipients using AppointmentItem.Resources property, then programmatically execute (Tools|Check Names) since the inspector is displayed:

set btn = inspector.commandbars.FindControl(1, 361)
btn.Execute

Dmitry Streblechenko (MVP)
http://www.dimastr.com/
OutlookSpy  - Outlook, CDO
and MAPI Developer Tool

 Yes indeed.
 Additionally, the recipient itself won't be added to the underlying unsafe appointment item.
 The only way I succeeded to add the recipient in a way that it will be reflected in the Outlook UI, is by using the Resources property.
 But in this case, the added resource is not resolve.
 Regards,
 Michael Zino

   "Dmitry Streblechenko (MVP)" <dmitry@dimastr.com> wrote in message news:#sM7NJ8#DHA.2636@TK2MSFTNGP09.phx.gbl...
   Are you saying that the code below produces an empty address?

   set Recip = SafeAppointment.Recipients.Add("resource1")
   Recip.Resolve(TRUE)
   MsgBox Recip.EntryID

   Also note that SafeAppointmentItem.Resources is readonly because OOM blocks
   reading of this property, writing is not blocked, hence you can set the
   Resources property on the original OOM AppointmentItem without a security
   prompt.

   Dmitry Streblechenko (MVP)
   http://www.dimastr.com/
   OutlookSpy  - Outlook, CDO
   and MAPI Developer Tool

   "Michael Zino" <mvidas@mercury.co.il> wrote in message
   news:u8qw0g3%23DHA.2476@TK2MSFTNGP12.phx.gbl...
   > Dear Dmitry,
   >
   > After resolving, the Recipient.Address and Recipient.EntryID are both
   empty
   > strings.
   > I am sure that this is a resolving issue, as the added resource is not
   > underlined and there is no free / busy information.
   > If I am using Tools | Check Names, the resource is resolved.
   >
   > My addin is manipulating the current AppointmentItem, which is currently
   > being displayed by the Outlook UI.
   >
   > I tried to add SafeRecipient into the SafeRecipients collection of the
   > SafeAppointmentItem, and to completely dereference and reopen the object
   and
   > still the SafeRecipient wasn't added to the appointment item.
   >
   > Additionally, I am wondering how I can access the SafeAppointmentItem's
   > Resources property, although it is read only property.
   > It seems that the only way of adding resources to the SafeAppointmentItem
   is
   > by using the Resources property, as other methods don't work at all.
   >
   > Regards,
   > Michael Zino
   >
   > "Dmitry Streblechenko (MVP)" <dmitry@dimastr.com> wrote in message
   > news:OIzsYxv#DHA.2012@TK2MSFTNGP11.phx.gbl...
   > How do you know that the resources cannot be resolved? After resolving,
   can
   > you access Recipient.Address and Recipient.EntryID properties? Note that
   > Outlook will not reflect in its UI any changes made through anything but
   the
   > Outlook Object Model until you completely dereference and reopen thne
   > object. Is m_oAppointmentItem displayed at the time your code is executed?
   >
   > Dmitry Streblechenko (MVP)
   > http://www.dimastr.com/
   > OutlookSpy  - Outlook, CDO
   > and MAPI Developer Tool
   >
   >
   > "Michael Zino" <mvidas@mercury.co.il> wrote in message
   > news:uEUx4Mr%23DHA.2292@TK2MSFTNGP12.phx.gbl...
   > > Hello,
   > >
   > > I am developing an Outlook addin using Redemption.
   > > I am trying to add recipients to the Outlook AppointmentItem as follows:
   > >
   > > Dim oSafeAppointment As Object
   > >
   > > Set oSafeAppointment = CreateObject("Redemption.SafeAppointmentItem")
   > > oSafeAppointment.Item = m_oAppointmentItem
   > > 'Note: m_oAppointmentItem was retrieved from OOM
   > >
   > > 'The following is not working; "Resource1" and "Resource2" are being
   added
   > > to the appointment but can't be resolved
   > > oSafeAppointment.Resources = "Resource1;Resource2"
   > > oSafeAppointment.Recipients.ResolveAll
   > >
   > > 'The following is not working as well
   > > Set oSafeRecipient = oSafeAppointment.Recipients.Add("Resource1")
   > > oSafeRecipient.Type = olResource
   > > oSafeRecipient.Resolve 'The problem is that "Resource1" isn't being
   added
   > to
   > > the appointment
   > >
   > > "Resource1" and "Resource2 exist and are being resolved automatically
   when
   > > they are being added manually through the Outlook UI or when using the
   > > following code:
   > >
   > > m_oAppointmentItem.Resources = "Resource1;Resource2"
   > > m_oAppointmentItem.Recipients.ResolveAll 'succeeded with security alerts
   > >
   > > Additionally, when I am using MAPIUtils and creating
   > > SafeRecipient--"Resource1" is resolved. But it can't help me, and I
   wrote
   > it
   > > just to make sure that the problem is not Exchange related:
   > >
   > > Dim oSafeRecipient As SafeRecipient
   > > Dim oUtils As Object
   > >
   > > Set oUtils = CreateObject("Redemption.MAPIUtils")
   > > Set oSafeRecipient = oUtils.CreateRecipient("Resource1")
   > > If oSafeRecipient.Resolved = True Then
   > >     Debug.Print oSafeRecipient.Name & "Resolved=True; Address=" &
   > > oSafeRecipient.Address
   > > End If
   > >
   > > Please advise.
   > >
   > > Regards,
   > > Michael Zino