When an email is sent out on Almabase, it is sent from a special email id that looks like john-doe@alumni.yourschool.org, instead of jdoe@gmail.com (which is the email that is listed on your profile page)

If an email is sent between 2 alumni, the receiver will see it in their inbox like this:
From: John Doe (john-doe@alumni.yourschool.org)
Reply to : john-doe@alumni.yourschool.org

The replies to this, are then automatically forwarded to the actual email address on their respective profiles (say, jdoe@gmail.com). This way, alumni can start conversations with others on the platform, without having to reveal their private email addresses.

Let's suppose the sender of the email was Marcus.
From: Marcus Williams(marcus-williams@alumni.yourschool.org)
Reply to :   marcus-williams+1234@alumni.yourschool.org

For bulk emails, any reply to the email will first come to marcus-williams+1234@alumni.yourschool.org, and then be forwarded to Marcus' real inbox (let's say it is mwilliams@gmail.com).

In a similar manner, when Marcus replies to that email, it will first be sent to a masked email that was generated by Almabase for the author of the first reply.

Not quite. when a reply or an email hits the Almabase system, the sender's email is looked up on your database. If no record has been found for that email, the email will not go through to the final recipient.

Eg: If someone named Greg tries to send an email to john-doe@alumni.yourschool.org ; Almabase first checks for Greg's email on your Almabase database.
If it exists - John will receive the email.
If it does not exist - John will not receive the email. Greg will subsequently get an automated reply from Almabase stating that he does not have sufficient permissions to email John.