E-mails sent from SingleOps should have a 'from' address on the singleops.com domain since e-mails sent from unverified and free e-mail addresses are more likely to be flagged as spam and rejected by your intended recipients (read more about signed e-mails here). However, e-mails sent through SingleOps will have a 'reply-to' address which reflects the e-mail address of the sender. This functionality is supported by all major e-mail clients.
Some e-mails may still come to your 'from' e-mail. Clients can copy the 'from' address manually or they may save it to their address book and send e-mails to it at some later time. For that reason, SingleOps allows you to configure your account to include the e-mail address to which you'd like to have replies sent.
You can configure the 'from' address in the SingleOps E-mail field on your account settings page (see screen shot below). This same page contains a field whereby you can configure to which address these e-mails should be forwarded. This can be any address you desire: your main customer contact e-mail address, your billing department, etc.