Error 56 While Sending an Email via SMTP Server

Solution

There are several factors that can cause Error 56. Perform the following operations to resolve this issue:

Allow LabVIEW to obtain access to the internet and add a firewall exception.
1. Open Firewall & network protection in your Windows PC.
2. Select Allow an app through firewall.
3. Scroll through the list of allowed applications and verify that LabVIEW is enabled for Domain, Private and Public.
4. If LabVIEW does not appear, launch LabVIEW and click Change settings from the top.
5. Select Allow another app...
6. In the pop-up window, select Browse...
7. Navigate to C:\Program Files (x86)\National Instruments\LabVIEW <version> and select the LabVIEW executable.
8. Click Add to close the pop-up window.
9. Click OK to close the Allowed apps window and save changes.
Check the status of your internet connection by directly pinging the SMTP server through Command Prompt.
1. Open Command Prompt.
2. Type in the following command: ping <SMTP server address>. For example, ping smtp.gmail.com
3. If the server can be reached, Command Prompt will display a reply as shown below.

Make sure the following ports are opened in your local network: 25 (SMTP), 465 (SMTP over SSL), 587 (SMTP Submission).
Some of the mailbox providers by default blocks 3rd party application access thought SMTP. Change these parameters in your mailbox settings if necessary.
- If using a gmail account, refer to [External] Enable Gmail Access for Non-Google Applications.