Please note that (clause)

Use this phrase to point out something that you want people to pay attention to in an email. You continue by explaining what you want your readers to pay attention to:

Please note that I will be out of the office starting Friday, September 2.

Please note that all applications must be accompanied by two letters of recommendation.

This is a very formal phrase. You can use this in public messages that you send or post to a large group of people, especially if you don't personally know all of them.

email service

"Email service" means the systems that send and receive email.

You mostly use this phrase in business settings:

What does your company use for email service?

(a system) is down

When a system is "down", it means that it's not working right now:

Oh, it looks like the Internet is down.

Systems that can "go down" include:

• phone networks
• websites
• a company's computer systems

There are some other systems that don't go "down", but instead go "out":

My electricity is out.

EST

"EST" is the abbreviation for a time zone. It is the time zone for the East Coast of the United States. So this time:

4pm EST

Means 4 o'clock in the afternoon on the East Coast of the U.S.

Some other time zones include:

• GMT - Greenwich Mean time, which is the time zone in Britain
• PST - Pacific Standard time, which is the West Coast of the U.S.

perform scheduled maintenance

When a company plans to do work to fix a system, they are going to do "scheduled maintenance".

A more formal verb that you can use with this phrase is "perform":

Sorry for the inconvenience. We are performing scheduled maintenance.

This phrase is common for talking about websites and computer networks.

Maintenance that is not planned ahead of time is "unplanned":

We're performing unplanned maintenance.

Or you might write something like this for an unexpected problem:

Our service is unavailable. We are working to resolve the issue as soon as possible.