Email Errors

If you experience errors when trying to Send Email, the information below may be helpful.

The most common reason for email errors is incorrect information entered in Email Setup. If sending email fails, follow these general steps:

Vendor specific issues:

Email Settings by Host

We have gathered settings for some email hosts. These settings may change at any time so always rely on the settings provided by your vendor.

Username Use SSL? Outgoing SMTP Server Outgoing Port Incoming POP3 Server Incoming Port
Gmail checked 587(required for outgoing encrypted email and SSL must be checked)465 works best for sending attachments 995
Alaska Communications checked 587 or 465 995
AOL checked 587
AT & T checked 465 995
Brinkster unchecked 25
Comcast checked 587
Einstein Medical checked 587 995
FatCow (Roundcube) checked 465
GoDaddy unchecked 25 or 465
Hotmail checked or 25 or 587 995
iCloud (Mozilla Thunderbird) checked 587
iCore checked 465
Just Host checked 465 995
Luxsci checked 587
Office 365 checked 587 993 or 995
Officite checked 587 995
Outlook checked 587 995
MSN Live checked 587
Optimum unchecked 25 unchecked 587
Prosites (Roundcube) checked 465 or 10465 or 11465
SendInc SendInc alias email address checked 465
Sesame unchecked 25 995
Solution 21 unchecked 25
TNT checked or 587 or 25 143
Verizon checked


Yahoo checked 465

Specific Errors & Solutions

If you receive any of the following errors, it means the username and/or password entered in General Email Settings is invalid.

Error: Mailbox Unavailable. The server responses was: #5.1.0 Address rejected.

Solution 1: Patient's email address is invalid. Send a test email to yourself to verify the message is only when using the patient's email address.

Solution 2: If sending from a new email address, check your inbox and open another email. This may activate the email address. Send another test to check.

Error: The operation has timed out.

Solution: Do some research and find out what port your email provider recommends, then try it. For example, for Gmail with SSL, port 465 has worked for sending emails with attachments.

Error: All confirmation emails failed.

Solution: This can happen if the subject line of the email mistakenly includes the body of the message. Check Setup Recall to make sure the subject line has a reasonable amount of words.

Error: Mailbox name not allowed. The server response was: sorry, that domain isn't in my list of allowed rcpthosts.


Error: Command not implemented. The server response was :5.5.41. Unrecognized command. z28sm22907yhn.7

Solution: In Email Setup, check the SSL box. Another possibility is to verify the password is correct. Some computers connected to the network and using the same email setup in Open Dental may be able to still use the email service if this box is unchecked.

Error: The remote certificate is invalid according to the validation procedure.

Solution: In Email Setup, uncheck the SSL box.

Error: Service not available, closing transmission channel.

Solution 1: Try a different outgoing port.

Solution 2: It could be caused by your antivirus software.

Error: Open Dental appears to have successfully sent email, but recipient never receives it.

Solution: Your mail server may block outgoing mail if too many emails are sent at one time. Contact your provider to change the setting.

Error: Email fails to send and an error message reads: "Transaction failed. The server response was: 5.7.1 <>: Recipient address rejected: Access denied.

Solution: SMTP server will not relay the message; this is usually due to an incorrect password.

Error: Keyset does not exist.

Solution: Run Open Dental as administrator.

Error: Mailbox unavailable. The server response was: (WS-SVR) []:12345 is currently not permitted to relay.

Solution: Contact your email domain provider and have them allow the relay from Open Dental.

Error: Error retrieving email messages: The stream used to retrieve responses from was closed.

Solution: Check your incoming email settings in Email Setup.

Error: Error retrieving email messages: The handshake failed due to an unexpected packet format.

Solution: This error can happen if your email address is not configured properly. Specifically, if your email account uses SSL and you do not have the SSL option enabled, or if you have SSL enabled and your email account does not use SSL. See Email Setup.

Problem: In the Email Inbox or Progress Notes, email preview and message is showing in HTML code.

Solution: This means the email was sent using Rich Text/HTML format instead of Plain Text.

Problem: An incoming encrypted message is not decrypted.

Solution: This happens when decryption fails. Usually decryption happens automatically when the message is received. However, if the email is from an address with a security certificate that is not trusted, your private decryption key is not installed on the local computer, or the encryption is not in the correct format, decryption fails. To see encrypted email options, see Email Encryption Options. To add a certificate to your trusted list or retry decryption. see Email Client, When Decryption Fails.

Error: Failed to send. Error message from the email client was: Failure sending mail.

Email hosts have a maximum attachment size when sending attachments from Open Dental. If the file size(s) are too large, the email will fail.


Error: The transport failed to connect to the server

Solution: Set the SMTP server to:

Error: The message could not be sent to the SMTP server. The transport error code was 0x80040217. The server response was not available

Solution: Yahoo is blocking "less secure" 3rd party applications. Create an App password for use with Open Dental.


Gmail outgoing encrypted emails will only work over port 587 with SSL enabled.

Error: Command not implemented. The server response was:5.5.1 Unrecognized command, s45sm17366386yhk.22 - gsmtp

Solution: In General Email Settings, change port 587 to 465.

Error: The message could not be sent to the SMTP server. The transport error code was 0x80040217. The server response was not available

Solution 1: In Email Address Edit, sign into google using Gmail Authorization (Sign in with Google button).

Solution 2: Verify user name and password (e.g. must include

Solution 3: Google is blocking account access from "less secure" 3rd party applications. See Google does not identify exactly what makes an application less secure, but offers two solutions: use the Gmail application instead or allow less secure apps. To allow less secure apps, log into Gmail. You should receive a message related to unauthorized access. Follow the instructions in the message to change your Gmail account settings to "Allow less secure apps".

Error: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required.

Solution 1: Enable less secure apps if you are using a regular Gmail account.

Solution 2: Change password to a more secure option.

Note: Gmail managed domains may not allow enabling of less secure apps. The domain administrator must login and give domain users the right to enable less secure apps.

Office 365

Error: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM.

Solution 1: Most likely, Office 365 needs you to create a new password. Log in to the Office 365 portal ( You will be prompted to change the password. Once the password is changed and reflected in Open Dental, email should work.

Solution 2: Make sure the email account in Open Dental has a valid Office 365 license assigned to it and that SMTP has been enabled for that account.

Note: By default, Office 365 may not have a license associated with a shared mailbox. Without a license SMTP cannot be enabled for the mailbox. If the solutions listed above do not work, we recommend contacting Office 365. If Office365 licenses have been purchased through another vendor, such as GoDaddy, you may need to contact the vendor to help with settings changes.

Alternatively: If the above does not solve the problem, try removing the Sender Address. Leaving this entry blank may allow the client to connect.

Error: 535 5.7.139 Authentication unsuccessful, SmtpClientAuthentication is disabled for the Tenant

When using Office 365 through GoDaddy.

Make sure SSL is checked, use GoDaddy's outgoing SMTP information and Office365's incoming POP3 information within the email address edit window


When trying to send emails in Open Dental using, receive Error: 5.7.3 Requested action aborted:user not authenticated.

Check your inbox for an email requesting permission to use Open Dental to send emails through Click the link in the email to activate Open Dental and allowing sending emails.


Error: Service not available, Not able to send message:

Solution: Use Port 587.


Error: The message could not be sent to the SMTP server. The transport error code was 0x800ccc6a. The server response was 451.

Solution: Update to the most recent version of Open Dental.