See this post on Custom forms:

It is often not necessary to use custom forms. It is a pretty quick fix to remove items with custom forms so they will replicate

The caveat to this is that those custom form items MAY not be the only ones which are not replicating if you manually moved things from a destination to a source.  See the end of this for that scenario.

The procedure to find out if you have custom forms: 

Go to the source folder in outlook

View in simple list

Right click on the header name field top of the columns

Select field chooser

Select contact type fields from the dropdown

Find Message Class

From the field chooser, select and drag the message class to the field names

You should now see the message class of all items (the form used) 

Normal Outlook contact form names are IPM.Contact and IPM.DistList for Contacts.  If it has IPM.Contact.SBE for example, it is a custom form

If you need the form, Exchange requires the form to be published to all destination locations of an Add2Exchange or Add2Outlook relationship.

You have two options, you can strip the form and use the normal default form or publish it to all locations.

Most of the time people just strip the form but your situation may require the use of the form because of some application you are continuing to use.

To publish the form to the different locations, review Microsoft’s Outlook Documentation: http://www.slipstick.com/developer/publishing-custom-forms/

To strip the form, you have a few options

 Use the Add2outlook Toolkit: http://support.diditbetter.com/downloads.aspx

The free option is to move all those items with the custom form in it to a sep folder of the same type; such as Custom Form Folder

Export those items to csv format.  TIP: Exporting will lose all attachments and pictures, if any, and any additional information from the custom form.

Then create a new temp folder of that type; such as Stripped Form Folder

Import the csv file into the new Stripped Form Folder

Then  copy those stripped items back into the Main folder and then start Add2Exchange or Add2Outlook and they will replicate.

TIP: You should be clear that if the custom form is continuing to be used, it will require the strip again or you must stop using the application with the custom form.

There are 3 paid options which may be attractive because they are in place form replacements and do not detach pictures or attachments.  These options will only lose any information contained in the additional fields of the custom form, as will any option to replace a custom form.

The first option is let us do this for you. We can do this for you and use any tools necessary as a Level 3 event, which is normally priced at $199.

The second option is the Diditbetter.com Software Forms Replacement tool you can also license for only $199. If you license this tool, we will remotely teach you how to use it, and you can run the tool at any time.

TIPS if you have manually moved stuff around :

Remember, once you have an Add2x relationship set up you can’t just manually copy things around anymore, especially taking from a destination and putting in as a source item because Add2Exchange will not copy a copy.  If this has been done, then finding out which ones are not copying and doing the process above for exporting and reimporting as if it had a custom form will also strip the A2E Copy tag off of them as well.  Those items will again be originals.

If finding out which items are not copying is difficult, the third option available to Add2Exchange users will solve the problem of making a copy an original again because you or the users have copied items around.  The export and import will work but you cannot have any Add2Exchange relationships replicating during this process.  Ideally a “Startover” should be performed.  Before the Startover,  a backup of any source items folders is required.

The Ad2Exchange Toolbox can do a Startover,  and the Surgeon General will also strip the A2E copy tag off of the manually copied items for an entire folder at one time.  The Add2Exchange Toolbox has to be licensed to have this startover and strip functions, and they are very powerful and should be used with supervision because if you have relationships set up and there SHOULD be copies in that folder, as is the case when you have the folder as a valid destination, running the tool can cause duplication after a replication.  Of course we offer the certified services to do this for you which do not require licensing any tools.