They should not record the IP in the first place. It looks like you are right about using a VPN on top of their email service according to this.
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Will using non-gmail hurt my chance of getting hired? -
Will using non-gmail hurt my chance of getting hired?Proton leaked a user's IP address to law enforcement, you should seek alternatives. source: https://arstechnica.com/information-technology/2021/09/privacy-focused-protonmail-provided-a-users-ip-address-to-authorities/