Server error when creating ultra-long email address

[ZeyuWang-cyber]

Prerequisites

• I have searched open and closed issues to make sure that the bug has not yet been reported.

Bug report

Describe the bug
I have added custom domain to my account. For example, my domain is hello.link. I added hello.link into my account and successfully created [email protected]. After that, I added subdomain kiwpu8stddaogrqf3tcrdy7mvo5sve3e9.svmap3e6ov5jxpsapgzmi43uzs5r3doa8bnqrqqy8i9ofkprjs6rugk2h76thxm.xxxxxxx-xxxxxx.xxxx.hello.link. I can add this subdomain to my account, but the website says server error when I try to create ultra-long email address. Server error happened when I tried to add email address hi@kiwpu8stddaogrqf3tcrdy7mvo5sve3e9.svmap3e6ov5jxpsapgzmi43uzs5r3doa8bnqrqqy8i9ofkprjs6rugk2h76thxm.xxxxxxx-xxxxxx.xxxx.hello.link to my account.

This ultra-long email address does follow RFC 3696.

I don't actually hold the domain hello.link. For privacy reason, I redacted some personal information.

Expected behavior

1. Show the limit of email address length.
2. Do not show server error message. Instead, the server has to tell me that this email address exceeds length limit.

Screenshots

Environment (If applicable):

• OS: Linux, Mac, Windows
• Browser: Firefox