Outlook 365 Custom forms field limit?

Not open for further replies.


New Member
Outlook version
Outlook 365 32 bit
Email Account
Office 365 Exchange

I have some custom forms which I built a few years ago which have worked without incident until the last few days. The first user reported that the forms weren't working yesterday morning but were working fine on Friday. When I checked yesterday I found I too was having issues. The forms reside in public folders. I have custom contact forms which still work fine and custom appointment forms which are the ones having issues.

We are all using Window 10 machines (updated from Windows 7 a couple weeks ago) and are O365 hosted Exchange. My current Office version is 16.0.16026.20146

When I go to save a custom appointment, I get the following error message:

"All custom fields cannot be created, because the allowed limit has been reached. For more information, contact your Microsoft Exchange Administrator."

When I go to open a custom appointment, I get the following error message:

"The custom form cannot be opened. Outlook will use an Outlook form instead. Unknown Error." followed by the error message:

"Sorry, we're having trouble opening this item. This could be temporary, but if you see it again you might want to restart Outlook. Unknown Error."

The following troubleshooting steps have been taken:
- Restart Outlook
- Reboot PC
- Clear Form Cache
- Repair Outlook (Quick and Online Repair)
- Deleted seldom used custom fields from Custom Appointment Form

I didn't see any Microsoft updates from over the weekend. Unsure where to go from here, but getting this working again would be very helpful.

Any assistance or suggestions would be greatly appreciated.

Thanks for your time,

Dave M
There isn't a limit on the number of fields but if I recall correctly, too many text fields can be a problem.

Do you have the form published to more than one folder or library?

When you cleared the cache, did you delete the forms subfolders in
C:\Users\diane\AppData\Local\Microsoft\FORMS ?
Do you know how many fields you have?

I checked with Karl Timmermans, the now-retired developer of contact genie.
if memory serves me correctly – the max number is 255. With that said, the other number that comes to mind is 192 for some reason keeping in mind that even the standard fields come into play. Lemme put it this way, if anyone comes even close to whatever the limit is – they gonna be in a world of hurt. Saw some really large custom forms in my time and none worked well on any level
Hi Diane,

Thanks for the quick reply. I didn't delete the subfolders in the FORMS folder when I renamed the cache. It's been a while since I've worked with these forms and couldn't remember if deleting them was an issue.

I don't think I am near the number of fields but I can go back and check that. I haven't done any type of development on these forms in probably 3 or more years so the field count has been the same since then. I find it odd that everything has worked fine for all this time and then all of a sudden, I have major issues.

We are looking to migrate this process to a PowerApp later in the year. I just need a couple more months.. lol
I have no idea what triggered it to fail now.

You could try saving the form in Froms manager as an FDM.

Do you have a backup copy of the form? Are there two copies published - one in the public folder, another in personal forms library or elsewhere?

Karl added this -
Will make 2 comments about this guy’s form without even seeing it and those are

#1 – If he got the error message “All custom fields cannot be created, because the allowed limit has been reached.” Then he needs to seriously go back to the drawing board and try and reorganize the form


#2 – His custom form is f*k’d (or both)

Either way – seriously doubt that he will be able to fix it. Other thing to keep in mind is a mistake a lot of people made which was to create custom fields using the standard Outlook field names which didn’t help things any – that and there was no real way to “remove” a field from the underlying form structure even when deleting it from the form via the UI.
Not open for further replies.
Similar threads
Thread starter Title Forum Replies Date
X Custom icon (not from Office 365) for a macro in Outlook Outlook VBA and Custom Forms 1
I Error saving screenshots in a custom form in outlook 2016, outlook 365 - ok in outlook 2013, outlook 2010 Outlook VBA and Custom Forms 5
H Custom autoforwarding, sending mail through outlook office 365 Using Outlook 1
I Create custom Outlook 2013 Rule in Office 365 Outlook VBA and Custom Forms 5
M does outlook 2013/365 on mac support custom forms? Outlook VBA and Custom Forms 1
M Start Outlook 365 at unified inbox Using Outlook 2
J Emails with .ICS calendar invitations attached don't contents when received in Outlook 365 Using Outlook 6
T Outlook 365 won't take new working password Using Outlook 0
P Yahoo/IMAP folder rename by Outlook desktop 365 Using Outlook 0
P VBA to add email address to Outlook 365 rule Outlook VBA and Custom Forms 0
Rupert Dragwater Background colors not saving in Outlook 365 Using Outlook 15
J Outlook 365 html inline images Using Outlook 0
Rupert Dragwater How to get Outlook 365 to open from websites Using Outlook 5
HarvMan Outlook 365 - Rule to Move an Incoming Message to Another Folder Using Outlook 4
TomHuckstep Remove Send/Receive All Folders (IMAP/POP) button from Outlook 365 Ribbon Using Outlook 2
A Outlook 365 Outlook (part of 365) now working offline - argh Using Outlook 5
G LinkedIn tab missing in Outlook 365 (but working in OWA) Using Outlook 0
P now on office 365 but getting error messages about missing Outlook 2013 cache folders Using Outlook 2
L Synch Outlook 365 calendar with iPhone Using Outlook 0
J Outlook 2016 Trying to get Outlook 2016 to work with Office 365 Using Outlook 0
L Duplicate calendar entries in Outlook 365 Using Outlook 3
G Stop Outlook 365 adding meetings to calendar Using Outlook 1
HarvMan Using Emojis in Outlook 365 Using Outlook 3
T Outlook 2019 Not Using Auto Compete After Deletion of 365 Using Outlook 1
CWM330 Is it me, or is Outlook 365 BUGGY? Using Outlook 3
K Outlook 365 After migrating to Outlook 365, some contacts display in emails with prefixes Using Outlook 0
HarvMan Outlook 365 loses "outlook.com" exchange server settings Using Outlook 1
D Office 365 Outlook desktop app prompts for all account passwords on startup Using Outlook 11
L Recommendations for Utility to Backup Outlook 365 Account Settings Using Outlook 2
Z New minimum Outlook for Windows version requirements for Microsoft 365/Exchange Online Using Outlook.com accounts in Outlook 27
kburrows Outlook 365 - Ribbon Customizations Disappear Using Outlook 0
C Why does Outlook (desktop) 365 for Windows keep making me input my passwords? Using Outlook 12
J Outlook 365 Outlook 2016/365 Contacts Lose Info when Favorited to the To-Do Bar Using Outlook 2
O Outlook 365 - Gmail and Outlook: how to force Outlook to start up in Gmail? Using Outlook 2
M Outlook 365 refuses to send email Using Outlook 0
P How can I stop Outlook 365 duplicating the posts? Using Outlook 1
HarvMan Toggle between calendar and email in Outlook 365 Using Outlook 12
S Mac Outlook 365 Questions Using Outlook 1
R Outlook 365 update sets delete from server flag Using Outlook 1
O Outlook 365 - How to create / copy a new contact from an existing one? Using Outlook 5
F Excel VBA to move mails for outlook 365 on secondary mail account Outlook VBA and Custom Forms 1
F Outlook 365 is "Possessed" Using Outlook 2
K Outlook Office 365 VBA download attachment Outlook VBA and Custom Forms 2
AmonRa Outlook 365 calendar - too much white space Using Outlook 0
G Outlook 365 with iCloud account not syncing calendars Using Outlook 2
L Ideas for Setup with New Office 365 Family Subscription (Outlook) Using Outlook.com accounts in Outlook 3
D Connecting Gmail to Outlook 365 - My Setup not working Using Outlook 2
Z Outlook 365 delete reminder you can’t make change to contents of this-read only folder Using Outlook 4
D Outlook 2016 how to use gmail account as source account for outlook 365 Using Outlook 9
M outlook 365 trying to finish my sentences Using Outlook 2

Similar threads