When using the mailFeed service you may wish to lock down which IP addresses are able to connect to your mail server via SMTP. This provides an added level of protection by preventing email being delivered directly to your server without passing through the mailFeed service. However, if choosing to do this please consider the impact of any clients that you have connecting remotely as they may require access to your SMTP server for sending email.
If locking down the IP addresses please ensure that you accept email from the following ranges:
- 193.203.117.0/24
- 185.54.85.0/24
- 178.32.81.96/28
In addition to locking down the IP addresses that may connect you should also ensure that SPF validation is disabled for emails originating from these blocks. This will ensure any local antispam software running within your environment does not generate a false-positive.