# hs\_object\_source\_detail\_3 with writable single send api v4

**URL:** <https://community.hubspot.com/t/hs-object-source-detail-3-with-writable-single-send-api-v4/146336>\
**Category:** APIs & Integrations\
**Tags:** email\
**Created:** [February 17, 2026, 3:27pm UTC](https://community.hubspot.com/t/hs-object-source-detail-3-with-writable-single-send-api-v4/146336 "2026-02-17T15:27:35Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![hkampen](https://d10pqhm3lwygmk.cloudfront.net/user_avatar/community.hubspot.com/hkampen/32/44643_2.png) [@hkampen](https://community.hubspot.com/u/hkampen)\
**Post date:** [February 17, 2026, 3:27pm UTC](https://community.hubspot.com/t/hs-object-source-detail-3-with-writable-single-send-api-v4/146336/1 "2026-02-17T15:27:35Z")

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Hi,

we are using hs\_object\_source\_detail\_3 on object creation and it works fine in direct creation, e.g. with contacts or companies, aswell with v3 endpoint /marketing/v3/transactional/single-email/send/

I now implemented /marketing/v4/email/single-send and I get the error

`„hs_object_source_detail_3“ ist eine schreibgeschützte Eigenschaft; ihr Wert kann nicht festgelegt werden.","errorType":"READ_ONLY_VALUE"`

I understand the field hs\_object\_source\_detail\_3 as write protected on update, not on creation.

Is the behaviour of the v4 API a bug or wanted? We need to know so we can handle it bevor the migration to v4.

Regards

Harald

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**Author:** ![Victor\_Becerra](https://avatars.discourse-cdn.com/v4/letter/v/87869e/32.png) [@Victor\_Becerra](https://community.hubspot.com/u/Victor_Becerra)\
**Post date:** [February 17, 2026, 5:30pm UTC](https://community.hubspot.com/t/hs-object-source-detail-3-with-writable-single-send-api-v4/146336/2 "2026-02-17T17:30:54Z")

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Hi there @hkampen and thank you for posting!

I found a few resources that should help clarify what’s happening with your issue

> **[HubSpot's default contact properties](https://knowledge.hubspot.com/properties/hubspots-default-contact-properties)**
>
> Learn more about the definitions of HubSpot's default contact properties.

> **[Accounts Dashboard | HubSpot](https://app.hubspot.com/myaccounts?next=developerdocs&redirect=%2Fapi-reference%2Fmarketing-single-send-v4%2Fguide)**

I’m also tagging a few community experts for additional ideas. Hey there @RubenBurdin @Josh @evaldas , I hope you’re having a great week! Any thoughts here?

Thanks  
Victor