How to save email adresses having weird, rare format?
Looks like the email validation inside CiviCRM does not like that pattern. If it is a valid email address that validation would have to be changed. You can do that yourself with a PR (https://docs.civicrm.org/dev/en/latest/core/contributing/) or at least raise it as an issue (https://docs.civicrm.org/dev/en/latest/tools/issue-tracking/#guidelines). Thanks!