I don't believe this is possible to wildcard as you describe.
I believe you will have to first export users to a all-users.CSV.
Then using the all-users.CSV, slim down and create a new update-users.CSV with the required columns for bulk administration and then include the optional column SmtpAddress_TextPager1. Required and Optional CSV options is listed in the URL's
In that optional SmtpAddress_TextPager1 column using excel magic to reference the alias column and concatenate "@x.com". Some formula simlar to =A1&"@x.com" This is assuming your alias matches the first part of your email addresses for all users of course.
Message notifications for the user are sent to this SMTP address.
Note that the SMTP address cannot include non-ASCII characters.
Finally, refer to the update-users.csv with the bulk administration to update users with mailboxes.
Have not tested myself but hope that helps you get started in a good direction.
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That's unfortunate. The method you describe works well for configuring many people at once. I used the same thing to initally turn on notification. It's adding new users that is a pain. We have a few people doing it and people some times get missed since we typically do an LDAP import there aren't a lot of settings that get adjusted.
I was looking for a way to modify the template using regex but couldn't find any support. I did come across the html templates in the newer versions of Unity. It looks like it is more flexible and might be able to do what you are looking achieve. It's under template/notifications templates