# Email with capital letter considered invalid

**URL:** <https://community.fibery.io/t/email-with-capital-letter-considered-invalid/741>\
**Category:** Bugs & Issues\
**Created:** [June 4, 2020, 2:15pm UTC](https://community.fibery.io/t/email-with-capital-letter-considered-invalid/741 "2020-06-04T14:15:27Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Haslien](https://sea2.discourse-cdn.com/flex020/user_avatar/community.fibery.io/haslien/32/493_2.png) [@Haslien](https://community.fibery.io/u/Haslien)\
**Post date:** [June 4, 2020, 2:15pm UTC](https://community.fibery.io/t/email-with-capital-letter-considered-invalid/741/1 "2020-06-04T14:15:28Z")

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Just used the API to batch up creation of multiple customer entities at once.

It seems like every customer that had a capital letter in their email caused an error, while the rest worked fine. I deleted every customer created, and tried again from the start with having it convert to lowercase before sending, which resulted in no errors.

Actually unsure if this lies with the middleware I am using ([unofficial-fibery JS client](https://gitlab.com/fibery-community/unofficial-js-client)) or the API.

 ![](https://us1.discourse-cdn.com/flex020/uploads/fibery/original/2X/b/b3f5edeb758c710c46576d67c721a1d2863a9cf4.png)

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**Author:** ![shotkin](https://sea2.discourse-cdn.com/flex020/user_avatar/community.fibery.io/shotkin/32/12_2.png) [@shotkin](https://community.fibery.io/u/shotkin)\
**Post date:** [June 8, 2020, 10:15am UTC](https://community.fibery.io/t/email-with-capital-letter-considered-invalid/741/2 "2020-06-08T10:15:02Z")

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Sorry for inconvenient error messages ☹  
We are working on clear error messages!

Our app needs following email invariant: all email letters should be lowercased.