Generating alias email addresses allows you to provide addresses you have complete power over to senders that you feel could be ill-intentioned or intrusive. But some communication from these senders may actually be important to you and you may even need at some point to reply to them and start a conversation.
Imagine you created an account on a website with an alias, and the service sends you an email about your account being compromised. You may need details about what this means for you and therefore need to reply to the email. However you probably want to stay in character and not break the anonymity and power over your inbox that the alias allowed you to have in the first place.
This is tricky, but Pocket Geek Privacy's Alias Manager allows you to do it.
Any reply to an email sent to one of your aliases will show the alias as the sender in the recipient’s email header and will not mention your private email address at all.
Of course it only works if the core of the message doesn't give you away by mentioning your private information! So make sure to sign with the username the service knows you by and to remove automated signatures if you use them. (These signatures are added automatically at the end of your emails and include contact information. They are common use in the professional world.)
Your email interface (Outlook, Gmail, Apple Mail, etc.) doesn't know that your private email address has been replaced by the alias associated with the external sender, because the switch happens after the email is sent. This is why, if you look in your "Sent" folder, you will see your private email address designated as the sender (in the "from" field) even though it is definitely NOT what the recipient will see in THEIR inbox!
An explanation banner is inserted on top of the emails that are sent to your alias email addresses. This banner is meant to let you know about the new reply feature and also to allow you to block senders directly from the email you just received. This banner, however, is removed when you reply to the email so you don't have to worry that it will give away the fact that you are using the service, and it won't pollute your communications.
If you find the "banner" too intrusive, you can opt out from seeing it by going to your "My Account" interface:
Go to My Account, or access it from the product directly (from the Settings): in the browser extension, open the Settings (from the Main Menu) and click on "Open My account" below your name; in the mobile apps, click on Settings and then "My account" below your name.
Go to "Preferences".
Uncheck the box next to "Display banner in emails".