Not sure if email is phishing attempt

People in the company just received a kinda odd email from the CTO of one of our main vendors.

 The email body text says  to please review attached document.  Then above the signature it repeats, 'Please see attached"  The email signature is different than he has sent in the past, but it uses company logos, and all of the info is correct.  So it could still be legit.  

There is a PDF attached to message.  It can't be opened "Couldn't open PDF" "Something's keeping this PDF from opening."

ESET AV does not find any malware with pdf attachment or email.   Reply-to is correct email address.  

 I see a lot of x-headers in the header info:  X-Microsoft-Antispam-Untrusted: UriScan, X-Forefront-Antispam-Report-Untrusted: SFV:NSPM

Is there any other analysis/steps I can do besides contacting the sender?
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Martin MillerCTOCommented:
Contact sender, possibly set up a rule to quarantine all incoming email from them until clarified.
JohnBusiness Consultant (Owner)Commented:
Almost for sure it is a phishing attempt. The document not working seems to be a giveaway.

As noted above quarantine the email until clarified
Shaun VermaakTechnical SpecialistCommented:
Goto and upload that PDF to check if it is malicious
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Scott CSenior EngineerCommented:
To be 100% sure contact the sender.  They will appreciate your diligence and also alerting them that they are being spoofed.

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Check the reply-to email address very carefully. Look for odd accents on any of the letters (easy to dismiss as a speck of dust on your screen) or for tricks such as a upper-case I being used in place of a lower-case L, like so: I l
In this example the second letter is the lower-case L.
Martin MillerCTOCommented:
Can we close this question ?
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