One important thing you must do for an SMTP Server is to add reverse DNS record on your Cloud Service.
To do this, first of all, you must install Azure Powershell, WindowsAzurePowershell.
Now, you must execute the following commands in PowerShell:
Azure Service Management(ASM)
Add-AzureAccount Select-AzureSubscription "subscription name" Set-AzureService -ServiceName "mycloudservice" -Description "SMTP Server Reverse DNS Record" -ReverseDnsFqdn "mycloud.cloudapp.net"
If you want to correct, Reverse DNS Record, you must run the following command,
Get-AzureService "mycloudservice"
Azure Resource Management (ARM)
Login-AzureRmAccount -SubscriptionId "aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee" Select-AzureRmSubscription -SubscriptionId "aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee" $p=get-azurermpublicipaddress -name "Public IP Name"-resourcegroupname "Resource Group Name" $p.dnssettings.reversefqdn = "domain name" set-azurermpublicipaddress -publicipaddress $p