Checking a value of a field matches against a large list of values


I am using plumsail forms to create a sign up form for our healthy lifestyle programmes that we deliver. To claim a free place on our programme, we must check whether their home postcode matches a list of postcodes we have (not sure on where best to store these yet). If the postcode matches, a user should be able to continue signing up. If the postcode does not match, then a message 'Unfortunately, we are unable to support people from your postcode' should be displayed and the user prevented from signing up.


The list of postcodes is currently ~120k. However, this list can be reduced down if we use just the 'outcodes'; i.e. the first 4 characters of the postcode. This reduces the list down to around ~150.


  1. Using full postcode to check will return the most accurate results and prevent any possibility of us supporting users that fall outside the postcode list. However, how would be best to store the values to check against using Plumsail forms? Are there any performance considerations here?

  2. The list of postcodes may increase over time as we begin to support more areas.

Field Names

Postcodes = 'Postcode'

I've looked through other community threads, however, most similar cases seem to be related to sharepoint forms and I do not think this resolves anything.

User Story

As a company
I want to check a users home postcode upon entry against a list of 'eligible postcodes'
So that we can ensure we only support users we are contracted to support and inform the user at point of entry they will not be eligible for the programme to prevent poor user experience.

Dear @BarcleyW,
This is quite an interesting request - where are the postcode values stored? It can definitely be done, we've done something similar recently for another company pulling data from Dynamics 365 - On-site construction forms with Dynamics 365 integration using Plumsail Forms

Please, contact us with your request at [email protected] - depending on where the values are stored, and how you want it to work, perhaps we can offer paid support or work together to create a user story for our blog, making sure you get this functionality working and the story can be shared with others.

Provide as much detail as possible, especially how you want to work technically, how the postcodes are stored, etc. - this will help with evaluation.

Hi @Nikita_Kurguzov,

Thanks your reply, sorry in the delay in getting back to you.

I will take a look at the link you've sent. We have different storage options. Microsoft Dataverse/Dynamics 365 is definitely a viable option. We have environments set-up for power apps we could utilise.

That would be fantastic. I will get in contact with support now.

Thank you!

Hi @Nikita_Kurguzov

I raised a support request to the email provided but have not heard anything back as of yet.

Is this something you'll be able to support with?

Many thanks,

Dear @BarcleyW,
Did you get an email back that your request was received and did you get a ticket #? If not, it might've been lost to spam, which happens very rarely.

If you did get a ticket # - please, let me know what the number is, so I can check. If you didn't, then try contacting us via this widget, it should work identical to an email after registration, but you can also see all your tickets - My tickets

Hi @Nikita_Kurguzov

I've just raised a request under #SP33054.

Thank you :slight_smile:

Dear @BarcleyW,
Thank you! I see the ticket, we'll reach out to you with more information in the ticket itself.