I’d look at the proxyaddresses, either in ADSI, or PowerShell / Attribute Editor

Get-ADUser -Identity $thatguy -properties proxyaddresses |
select -expandproperty proxyaddresses

Oh so it has the wrong email listed in the GAL ?You probabaly need to update the Primary SMTP address ( primary is where the SMTP is capitalized), again, check the proxyaddresses.

EDIT: Ugh shpellynk

2 Spice ups