In these days I came across with an old problem in a customer, all my processes stopped sending e-mails. In the past I already had this problem when I was on vacations but before my return all starts to work and because of this I never investigated that problem, so I thought “tonight is the night”.
I began to investigate the problem executing a query in the msdb DataBase that allowed me to see the logging of all emails that I was trying to send:
order by 1 desc
And the error output was:
“The mail could not be sent to the recipients because of the mail server failure. (Sending Mail using Account 8 (2015-12-20T23:14:43). Exception Message: Cannot send mails to mail server. (Failure sending mail.).)”
Next step: validate the SMTP Server…
To do that you have to go IIS6
Then, go to properties in SMTP Server
Doing that I noticed that in the tab Access, option “Connection” I was blocking all the IP Adresses with an exception of my virtual machine IP.
It appears all right but I decided to try the selection “All except the list below” and retry to send a new test email. After doing that I was able to send emails again.
Cause of this issue:
My machine is an Azure Virtual Machine that doesn't have a dynamic internal IP. When I did a restart to the machine the IP was changed and because of that this machine was not allowed to access the SMTP Server.
Solution 1: Keep the option that all computers can access to this SMTP server
Solution 2: Change the VM to use a static internal IP Adress and put again the option “Only the list below”
Solution 3: Select “Only the list below” but using a domain instead of the IP