“An attempt was made to access a socket in a way forbidden by its access permissions” while using SMTP

Question

I am trying to send an SMTP email when certain values in database crosses its threshold value.

I have already allowed ports 25,587 and 465 in the Windows firewall an

Answer 1

Windows Firewall was creating this error for me. SMTP was trying to post to GMAIL at port 587. Adding port 587 to the Outbound rule [Outbound HTTP/SMTP/RDP] resolved the issue.