# Replying to a V2 message with the V3 API creates a new thread

**URL:** <https://forums.nylas.com/t/replying-to-a-v2-message-with-the-v3-api-creates-a-new-thread/528>\
**Category:** Question and Answers\
**Tags:** email-api, webhooks\
**Created:** [October 20, 2024, 11:52pm UTC](https://forums.nylas.com/t/replying-to-a-v2-message-with-the-v3-api-creates-a-new-thread/528 "2024-10-20T23:52:59Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![vincentg](https://avatars.discourse-cdn.com/v4/letter/v/a587f6/32.png) [@vincentg](https://forums.nylas.com/u/vincentg)\
**Post date:** [October 20, 2024, 11:53pm UTC](https://forums.nylas.com/t/replying-to-a-v2-message-with-the-v3-api-creates-a-new-thread/528/1 "2024-10-20T23:53:00Z")

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Hi,

We are currently in the process of migrating from the Nylas V2 to V3 API. We are currently grouping messages by thread ID and are encountering an issue where we are unable to reply to a V2 message with the V3 API (`reply_to_message_id `). As a result it is creating a new thread.

As a solution we were thinking of adding a custom header with the V2 thread ID when sending using the V3 API and then mapping back when receiving the message webhook but it turns out custom headers are not sent back.

TLDR, there are 2 questions here:

- How do we reply to a V2 message ID with the V3 API and retain the original thread ID to have a smooth migration for our users
- If not possible, what would be the best approach to resolve this?

Thank you,

Vincent

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**Author:** ![spang](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.nylas.com/spang/32/218_2.png) [@spang](https://forums.nylas.com/u/spang)\
**Post date:** [October 21, 2024, 4:51pm UTC](https://forums.nylas.com/t/replying-to-a-v2-message-with-the-v3-api-creates-a-new-thread/528/2 "2024-10-21T16:51:39Z")

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hi @vincentg, this sounds like it could be a bug. Can you please submit a support ticket through the dev portal with more information on what you are encountering?

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**Author:** ![vincentg](https://avatars.discourse-cdn.com/v4/letter/v/a587f6/32.png) [@vincentg](https://forums.nylas.com/u/vincentg)\
**Post date:** [October 21, 2024, 10:17pm UTC](https://forums.nylas.com/t/replying-to-a-v2-message-with-the-v3-api-creates-a-new-thread/528/3 "2024-10-21T22:17:14Z")

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Hi Spang,

Which part would be a bug? Creating a new thread ID on reply or not receiving custom headers in webhooks?

Thanks,

Vincent

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<div class="post-metadata">

**Author:** ![spang](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.nylas.com/spang/32/218_2.png) [@spang](https://forums.nylas.com/u/spang)\
**Post date:** [October 23, 2024, 3:38pm UTC](https://forums.nylas.com/t/replying-to-a-v2-message-with-the-v3-api-creates-a-new-thread/528/4 "2024-10-23T15:38:06Z")

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Creating a new thread ID on reply