Xerox “016-764 / 016-765” — SMTP auth failed (Scan to Email)

Joe B.

Reviewed for technical accuracy

Specialities: Xerox MFPs, Scan to Email, Microsoft 365/Google Workspace, SMTP/TLS, Firewalls & DNS

Fix Xerox SMTP authentication errors — Office 365 (Exchange Online), Gmail app password, ports 587/465, STARTTLS/TLS, OAuth2/basic

Technician

Hey! We’ll get Scan to Email working and clear Xerox error 016-764 / 016-765 — SMTP authentication failed.
A few checks: Which mail system are you using (Microsoft 365/Exchange Online, Gmail/Google Workspace, on-prem Exchange/SMTP relay, or ISP SMTP)? Do you sign in with a mailbox user & password, or send through a relay with IP allow-list? Also share which model (VersaLink/AltaLink/WorkCentre) and the current SMTP server, port (587/465/25) and security (STARTTLS/SSL) you set.

Customer

It’s a VersaLink C405. We use Microsoft 365. SMTP server is smtp.office365.com on port 587 with STARTTLS. Username is the shared mailbox address. Error shows 016-764 or sometimes 016-765 every time I try to scan.

Technician

Got it. Those codes mean the MFP reached the SMTP server but the login or TLS negotiation failed. With Microsoft 365 the common causes are:
• Using a shared mailbox credential instead of a licensed user or mail-enabled security group + connector.
• Modern authentication (OAuth2) required, but the device is set for basic auth with username/password.
• Wrong from address (must match the signed-in user when using authenticated SMTP).
• Time skew, DNS, or certificate trust breaking STARTTLS.
We’ll choose one of two stable paths: Authenticated SMTP (port 587 + STARTTLS) with a mailbox user, or Microsoft 365 SMTP relay via your public IP.

Customer

We prefer username/password. The account has MFA on. Could that block the printer?

Technician

Yes—MFA blocks basic SMTP. Options:
Option A — Authenticated SMTP with app password
1) Enable Authenticated SMTP (SMTP AUTH) for that user in the Microsoft 365 admin center.
2) Create an app password under the user’s Security info.
3) In the Xerox web UI (Properties → Apps → Email → SMTP), set server smtp.office365.com, port 587, security STARTTLS, and sign-in as user@domain.com with the app password.
4) Set From address = the same user. Test.

Option B — Microsoft 365 SMTP relay
Create an Exchange Online connector, allow your public IP, and use your domain’s MX as the Smart Host. In Xerox choose “No Authentication”, port 25, TLS if required. This is great for devices without user credentials.

Customer

What about Gmail/Google Workspace? Our other site uses Gmail and sees the same 016-764 code.

Technician

For Gmail:
• Server smtp.gmail.com, port 465 with SSL/TLS (or 587 with STARTTLS).
• Use a mailbox that has 2-Step Verification enabled and create an app password for “Mail”. Regular passwords + “Less secure apps” no longer work.
• In Xerox set From Address to that same user. Many rejections happen when the from address doesn’t match the authenticated account.
This clears 016-764 / 016-765 in most Google cases.

Customer

We use a local Exchange server at HQ. Port 25 with TLS. Could certificates or time settings cause this?

Technician

Absolutely. For on-prem relays:
• Ensure the root/intermediate CA that issued your SMTP certificate is trusted by the Xerox (upload under Security → Certificates → Trusted CA).
• Sync device time via NTP (wrong clock breaks TLS).
• Confirm DNS resolution and firewall allow-lists (25/587/465 outbound).
• If the relay is IP-based, choose “No Authentication” and match the MFP’s static IP in the server’s receive connector. If authenticating, set LOGIN/PLAIN with the proper UPN (user@domain.com).
• Some sites require Maximum message size tweaks—set scan size under Email → Message Settings.

Customer

I entered the app password but still get 016-765. Any other Xerox settings I should review?

Technician

On VersaLink/AltaLink check these:
• SMTP – Device Email Address equals the authenticated user (for O365/Gmail).
• Login Name format: use full user@domain.com, not just the alias.
• Connection Encryption: choose STARTTLS (587) or SSL/TLS (465) to match your provider.
• Disable Validate Server Certificate only for testing—prefer uploading the correct CA instead.
• Clear any cached credentials and reboot the device (some firmware holds old auth tokens).
• Update to latest firmware; older builds fail modern ciphers/SNI.

Customer

We also want to send from a “noreply@domain.com”. Can the Xerox do that with O365?

Technician

With Authenticated SMTP, Exchange Online requires the From to match the signed-in user. To send as a shared or “noreply” address, either:
• Assign the device user Send As permission on that mailbox and use the mailbox as the login, or
• Use the SMTP relay connector (IP allow-list) so the device can send from your domain without user auth.
The relay method avoids MFA and is best for multiple from addresses.

Customer

After switching to app password and matching the From address, the test passed. Any final checks so this stays fixed?

Technician

Final checklist for 016-764 / 016-765 avoidance:
• Lock the device to a static IP and working DNS (use your internal DNS or 1.1.1.1/8.8.8.8).
• Enable NTP time sync.
• Limit scan size (e.g., 10–20 MB) and choose PDF/MRC compression.
• If your firewall does SSL inspection, bypass the Xerox for smtp.office365.com / smtp.gmail.com.
• Document the credentials/app password in your IT vault. If the password rotates, update the MFP the same day.

Customer

Perfect — scans are emailing again and no more 016-764/016-765 errors. Thanks!

Technician

Summary: Xerox 016-764 / 016-765 — SMTP authentication failed is fixed by matching your mail platform’s requirements: O365 app password + SMTP AUTH (587 STARTTLS), Google app password (465 SSL/TLS), or a Microsoft 365 SMTP relay with an IP allow-list. Verify From address, certificates, NTP, and firewall. Need hands-on help? Open the chat.

Quick answer: the accepted fix

Accepted fix when Xerox shows 016-764 / 016-765 (SMTP authentication failed): use the correct method for your provider—Microsoft 365 with SMTP AUTH enabled + app password on port 587 STARTTLS; Gmail/Google Workspace with app password on 465 SSL/TLS; or a SMTP relay connector with IP allow-list. Match the From address, sync time (NTP), and trust the server certificate.

FAQ

Step-by-step (Xerox web UI)

1. Open the device’s web page → Properties → Apps → Email → SMTP.
2. Choose your provider: smtp.office365.com:587 STARTTLS or smtp.gmail.com:465 SSL/TLS (or your relay host/port).
3. Set Authentication as required. For O365/Gmail use mailbox user@domain.com with an app password. For relay, choose No Authentication and allow the MFP IP on the server.
4. Set Device From Address to match the authenticated account (or an address allowed by your relay).
5. Under Connectivity → NTP/DNS, enable time sync and working DNS. Upload needed trusted CA certificates.

Notes for mixed environments (networks & security)

1. Bypass SSL inspection for smtp.office365.com and smtp.gmail.com.
2. Allow outbound TCP 25/465/587. Some ISPs block 25; use 587 or a relay.

Sources

• Microsoft — Set up devices/apps to send mail with Microsoft 365
• Google — Send email from a printer/scanner using Gmail
• Xerox Support — VersaLink/AltaLink Email (SMTP) setup

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