In order to narrow down your issue and exclude the UiPath Studio cause, open a PowerShell console and check the below scripts. If they are working and you can send and receive the emails, that means some configuration in UiPath Studio is the issue. If not, double-check the SMTP server credentials.
With credentials, SSL, and an attachment:
$From = "USER.NAME@gmail.com"
$To = "USER.NAME@uipath.com"
$Cc = "USER.NAME@gmail.com"
$Attachment = "C:\Marian\policies.txt"
$Subject = "Email Subject"
$Body = "Insert body text here"
$SMTPServer = "YOUR_SMTP_SERVER_ADDRESS"
$SMTPPort = "YOUR_SMTP_PORT_NUMBER"
$username="YOUR_SMTP_USERNAME"
$password = "YOUR_SMTP_PASSWORD" | ConvertTo-SecureString -AsPlainText -Force
$credential = New-Object System.Management.Automation.PSCredential($username, $password)
Send-MailMessage -From $From -to $To -Cc $Cc -Subject $Subject `
-Body $Body -SmtpServer $SMTPServer -port $SMTPPort -UseSsl `
-Credential $credential -Attachments $Attachment
Without credentials and SSL:
$From = "USER.NAME@gmail.com"
$To = "USER.NAME@uipath.com"
$Subject = "Email Subject"
$Body = "Insert body text here"
$SMTPServer = "YOUR_SMTP_SERVER_ADDRESS"
$SMTPPort = "YOUR_SMTP_PORT_NUMBER"
Send-MailMessage -From $From -to $To -Subject $Subject `
-Body $Body -SmtpServer $SMTPServer -port $SMTPPort