Drain the mail queues on the server.

I want to put the Exchange 2016 server into maintenance mode before rebooting it. The first command is to  Drain the mail queues on the server.  

Set-ServerComponentState EX16-1 -Component HubTransport -State Draining -Requester Maintenance

Question:  What does it mean by draining the mail queues.  What would this command do on server? I want to understand it practically . Can some one explain please.
Muhammad AsifSenior Solutions ArchitectAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Todd NelsonSystems EngineerCommented:
From a high level, "draining" essentially refers to pushing the messages from that server's queue to one of the other active servers in the DAG so the outbound messages will get delivered normally if the maintenance window takes longer than expected.
Adam BrownSr Solutions ArchitectCommented:
When you set the queues to drain, they'll stop accepting mail and finish processing whatever mail is in the queue. This keeps you from losing or delaying mail during maintenance. In this case, you are tagging one of the servers as being in maintenance mode, which shuts down the transport service on the server so it does not accept SMTP or x.500 messages for delivery on that server. This will cause any servers that are attempting to send to that server to do one of these options:
1. deliver to whichever server is on the next priority MX record
2. hold on to the message and await restored service on the server
3. route messages through a different server

Usually it'll be number 2.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.