With the Links interface now deprecated in the Outlook 2013 Interop, a lot of people still want to be able to link contacts.

If you wish to do so and are willing to go the extra mile, you should be able to link contacts by setting/modifying these four properties using Extended MAPI:

1. http://schemas.microsoft.com/mapi/id/{00062008-0000-0000-C000-000000000046}/853A101E

2. http://schemas.microsoft.com/mapi/id/{00062008-0000-0000-C000-000000000046}/8586001E

3. http://schemas.microsoft.com/mapi/id/{00062008-0000-0000-C000-000000000046}/85850102

4. http://schemas.microsoft.com/mapi/id/{00062008-0000-0000-C000-000000000046}/85840102

Here is an example for a contact called Mellissa MacBeth that has Mellissa MacBeth 1 and Mellissa MacBeth 2 linked to it:

PidLidContactLinkName :
Mellissa MacBeth 1; Mellissa MacBeth 2

PidLidContactLinkEntry :
02000000E80000006D00000000000000FE42AA0A18C71A10E8850B651C24000003000000040000000000000046000000000000001C03AAABB26B2D45B0FFE66E8EADD9F9070032C4774090800941AAD28EE30284A19D00000000010F000032C4774090800941AAD28EE30284A19D00000005889F0000000000753D456D00000000000000FE42AA0A18C71A10E8850B651C24000003000000040000000000000046000000000000001C03AAABB26B2D45B0FFE66E8EADD9F9070032C4774090800941AAD28EE30284A19D00000000010F000032C4774090800941AAD28EE30284A19D0000000588A00000000000000000

The value breaks down into :

Flat Entry List
cEntries = 2
cbEntries = 0x000000E8

Entry[0] Size = 0x0000006D
Contact Address Book / PDL Entry ID:
abFlags = 0x00000000
Provider GUID = {0AAA42FE-C718-101A-E885-0B651C240000} = muidContabDLL
Version = 0x00000003 = CONTAB_VERSION
Type = 0x00000004 = CONTAB_USER
Index = 0x00000000 = EEI_EMAIL_1
EntryIDCount = 0x00000046
Exchange Message Entry ID:
abFlags = 0x00000000
Provider GUID = {ABAA031C-6BB2-452D-B0FF-E66E8EADD9F9} = Unknown GUID
Message Type = 0x0007 = eitLTPrivateMessage
Folder Database GUID = {4077C432-8090-4109-AAD2-8EE30284A19D} = Unknown GUID
Folder GlobalCounter = cb: 6 lpb: 00000000010F
Pad1 = cb: 2 lpb: 0000
Message Database GUID = {4077C432-8090-4109-AAD2-8EE30284A19D} = Unknown GUID
Message GlobalCounter = cb: 6 lpb: 00000005889F
Pad2 = cb: 2 lpb: 0000
Unparsed data size = 0x00000003
cb: 3 lpb: 000000
Entry[0] Padding:
Unparsed data size = 0x00000003
cb: 3 lpb: 753D45

Entry[1] Size = 0x0000006D
Contact Address Book / PDL Entry ID:
abFlags = 0x00000000
Provider GUID = {0AAA42FE-C718-101A-E885-0B651C240000} = muidContabDLL
Version = 0x00000003 = CONTAB_VERSION
Type = 0x00000004 = CONTAB_USER
Index = 0x00000000 = EEI_EMAIL_1
EntryIDCount = 0x00000046
Exchange Message Entry ID:
abFlags = 0x00000000
Provider GUID = {ABAA031C-6BB2-452D-B0FF-E66E8EADD9F9} = Unknown GUID
Message Type = 0x0007 = eitLTPrivateMessage
Folder Database GUID = {4077C432-8090-4109-AAD2-8EE30284A19D} = Unknown GUID
Folder GlobalCounter = cb: 6 lpb: 00000000010F
Pad1 = cb: 2 lpb: 0000
Message Database GUID = {4077C432-8090-4109-AAD2-8EE30284A19D} = Unknown GUID
Message GlobalCounter = cb: 6 lpb: 0000000588A0
Pad2 = cb: 2 lpb: 0000
Unparsed data size = 0x00000003
cb: 3 lpb: 000000
Entry[1] Padding:
Unparsed data size = 0x00000003
cb: 3 lpb: 000000

PidLidContactLinkSearchKey :
0200000028000000100000004F7EE07206ADA94485FE7075FBBACA9210000000331330D2D7A7564DA0B1EB608E7AE750

PidLidContacts :
0 : Mellissa MacBeth 1
1 : Mellissa MacBeth 2

If time allows it I will try and write a sample for this.