This article was previously published under Q290783
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There is no exact limit to the number of fields and controls you can use on a custom Outlook form, but Microsoft Product Support Services recommends that custom Outlook forms have fewer than 300 controls or user-defined fields, otherwise the form may not function correctly.
IMPORTANT: Although you should always create backups of a solution while it is being developed, if your form uses more than 200 fields or controls you should be extra vigilant in keeping backups.
When designing an Outlook form, you can add controls and user-defined fields to the form. In addition, you can link, or bind, the two together so that the data in the field is displayed in the control.
Outlook is designed to not have any set limits on a form's size. However, due to limitations of various software components -- both internal and external to Outlook -- forms will eventually encounter a limitation when a certain amount of controls or fields are added and you use the form in a particular way.
When problems occur with very large forms, they usually occur when you publish the form, send an item, save an item to a folder, save the form as an Outlook template (.oft), or use the Advanced Find feature on items with many custom fields. However, other scenarios may also encounter problems with very large forms or items.
Based on problem reports from customers, Microsoft Product Support recommends that forms not exceed 300 fields or controls.
NOTE: Customers have successfully created items with greater than 500 fields, but these forms had a limited number of controls. Likewise, you could theoretically create a form with more than 300 controls, but controls typically require fields to store the data associated with the controls.
There are many combinations of variables that play a role in determining when you may reach a custom form limitation. Most notable are the following:
The size (in bytes) of each control on the form. Various controls will take different amounts of storage space.
The size (in bytes) of each field on the form. Various field types may require different amounts of storage space.
The properties stored as part of each control, including the control name.
The amount of data stored within each field.
Whether or not a control is bound to a field.
Where the form or item is published or stored, such as in a Microsoft Exchange Server folder, or a local Personal Folders (.pst) file.
The type of form you are using. For example, a standard contact form is larger than a standard mail message form.
Any form-level properties, such as those located on the Properties page of the form.
The version of Outlook you are using. For example, the standard Outlook 2000 contact form is larger than the standard Outlook 97 or Outlook 98 contact form.
Whether or not the form has any attachments.
Whether the form uses nested container controls, such as the MultiPage or Frame controls, where a nesting-related limitation may arise.
The operating system you are using, and perhaps other system-related components such as network protocols.
The following suggestions may help by either increasing the amount of fields or controls you can use on your form, or by reducing the total number of fields you want to use.
Redesign the solution so that more than one form is used to store the data.
Minimize the length of field and control names.
Try to consolidate data into fewer fields. In some cases, it may be possible to programmatically store multiple fields into one field. You could programmatically parse the data when the form is opened, assign the data to controls, let the user use the form, retrieve the data from the controls, and then concatenate the data when the form is closed.
Reconsider where your data is being stored. Large amounts of data may be more suitable in a relational database such as Microsoft SQL Server, Microsoft Access, or Microsoft FoxPro. Or, you may be able to store primary field information in Outlook fields and secondary information in external databases.
Frequently back up your form if it contains more than 200 fields or controls. You should save and keep separate Outlook template files as you go (form1.oft, form2.oft, and so forth) in addition to publishing and keeping multiple versions in a folder (preferably on a Microsoft Exchange Server).
For additional information about form size limitations, click the article numbers below to view the articles in the Microsoft Knowledge Base:
290781 OL2002: Text That You Insert into Field Is Missing
290784 Error message when you publish a large custom Outlook form that contains many controls or user-defined fields: "Unable to successfully publish the form due to a MAPI error"
197145 PRB: E_FAIL on SaveChanges() with Too Many Properties
For additional information about available resources and answersto commonly asked questions about Microsoft Outlook solutions, click the article number below to view the article in the Microsoft Knowledge Base:
287530 OL2002: Questions About Custom Forms and Outlook Solutions