If you try to enter a support email address for the portal in this dialog that has a top level domain name (the part of an email address to the right of the last period) that is more than 3 characters Service Manager will put a red box around it telling you that it is invalid and won’t let you submit the form:
Sure – nearly all of the real top level domain names in the world are three characters or less but not all of them such as .info, .museum, etc. and some people like to use .local for a locally configured test domain (as above). As of last month the ICANN approved the first non-Latin top level domain names. I have no idea how Service Manger’s self-service portal would deal with that.
The workaround is to update the ServiceManager DB directly using T-SQL something like this:
update MT_Microsoft$ServiceManager$Portal$ContactSettings set EmailAddress_56B0CC85_71C4_4BDC_8AAB_61E4C4AACC0A = 'test@test.local'
Note: after you do this you won’t be able to submit changes to the other contact information using the form in the UI anymore so make sure you set all of those first and then do this (or just do it over again if you need).