Microsoft Exchange: The properties on this object have invalid data.

Firstly we need to identify what is causing the issue - so we can review the distribution group with something like:

Get-DistributionGroup "Testing(123)" | FL

and ensure there are no invalid objects within that group with something like:

Get-DistributionGroupMember "Testing(123)" | FL

In my event after issuing the first command I was presented with the following warning at the bottom of the output:

WARNING: The object mydomain.int/Users/Alerts has been corrupted, and it's in an inconsistent state. The following validation errors happened: WARNING: Property expression "Testing(123456)" isn't valid. Valid values are: Strings formed with characters from A to Z (uppercase or lowercase), digits from 0 to 9, !, #, $, %, &, ', *, +, -, /, =, ?, ^, _, `, {, |, } or ~. One or more periods may be embedded in an alias, but each period should be preceded and followed by at least one of the other characters. Unicode characters from U+00A1 to U+00FF are also valid in an alias, but they will be mapped to a best-fit US-ASCII string in the e-mail address, which is generated from such an alias.

It looks like the object had not been upgraded and was orginially created as an older version that accepted the parethnesis in alias names, although Exchange 2010 did not like this.

So to resolve the issue I simply reset the alias with something like:

Set-DistributionGroup "Testing(123)" -Alias "Testing123456"