YAPI shows error message "Failure sending mail".
The typical cause of this problem is the firewall that blocks YAPI connection to our email server smtp.sendgrid.net on port 587. Please note that it could be a local firewall (Windows Firewall, your antivirus software firewall, proxy settings, etc) or your office peripheral firewall like SonicWall, etc.
At first, check YAPI Email Configuration. Go Setup and Manage, Global Setup, Email tab
Please make sure that Use YAPI Email Service button is checked.
To troubleshoot this problem start with the simple connection test:
Launch Windows command prompt and type
telnet smtp.sendgrid.net 587
then hit Return key.
Normally you will see the following response from email server showing successful connection.
But most likely you will see this response that indicates that connection attempt was blocked.
Check your firewalls and antivirus software. Repeat the test.
The following response indicates that telnet.exe is not available on your computer.
In such a case you need to enable Windows Telnet Client software then repeat the test
Note, that if you are using a secure email provider port 465 must be opened as well.
Here is the list of all internal and external ports that YAPI is using. Please make sure that those ports are not blocked by the firewall.