How to Limit Email Size in Exchange Server for Better Performance
You can limit email size in Exchange Server by setting message size rules for the organization, connectors, and mailboxes. These rules help your server perform more efficiently and prevent issues with sending emails. They also ensure compliance with company policies. Many organizations use the default limits, commonly setting 10 MB for sending and receiving emails. The table below outlines the usual default limits in Exchange Server and Exchange Online.
Key Takeaways
Limiting email size in Exchange Server helps it run faster. It also stops crashes from big messages.
Set size limits for the whole group, connectors, and mailboxes. This helps control emails and keeps the server safe.
Use Exchange Admin Center or PowerShell to see current limits. You can also change and check settings easily.
Test new size limits by sending emails close to or over the limit. This makes sure blocking and delivery work right.
Tell users about changes in a clear way. Watch email flow often to keep Exchange Server safe and working well.
Why Limit Email Size
Performance Impact
Setting limits on email size in Exchange Server helps your system work better. Big emails can slow down the server and make everyone wait longer. If you let people send huge emails, the server uses more CPU, memory, and storage. This can make emails take longer to send and might even crash the system.
Exchange Server needs a lot of RAM to handle emails. Really big emails use even more memory, which slows down other jobs.
Large emails take up more disk space. If the server runs out of space, it cannot process new emails.
Lots of big emails can overload the Exchange Transport Service and make the CPU work too hard.
If the server gets too busy, it may turn on "back pressure." This stops or slows down emails to keep the server safe.
Tip: Microsoft says to set a 10MB message size limit. This keeps your system steady and stops it from running out of resources.
In virtual servers, big emails can make things worse. Exchange might spend more time on resources than sending emails. This can cause delays and make fixing problems harder. Setting good size limits keeps your server fast and dependable.
Security and Compliance
Limiting email size also keeps your organization safer and helps you follow rules.
Big attachments can hide malware or viruses. If people are not careful, they might open bad files.
Large emails are easier for attackers to use in denial-of-service attacks. These attacks can fill up your server and stop emails.
Emails with big attachments use more bandwidth and storage. This costs more money and slows down your network.
Some rules, like HIPAA and the CCPA, say you must protect sensitive data. Limiting email size helps you control what leaves your company.
Spam filters often block emails with certain files or big attachments. Using links instead of attachments can help emails get through and follow the rules.
Note: Teach your users about safe email habits. Use secure file-sharing tools for big files. This keeps your data safe and helps you follow the law.
Check Current Limits
You should look at your message size limits before making changes. This helps you know what is set up now. Then you can see if you need to change anything.
Exchange Admin Center
The Exchange Admin Center (EAC) lets you see mailbox size and message limits. Here is how you do it:
Open your browser and go to
https://admin.exchange.microsoft.com/
.
Click Recipients and pick Mailboxes.
Pick the mailbox you want to check. A new page will show up on the right.
On the General tab, find the Mailbox Usage section. You will see the mailbox size and limits here.
You can also check message size limits for connectors and the organization in the EAC. Go to Mail Flow and then Connectors. Pick a connector to see its settings, like the biggest message size.
Looking at these settings in the EAC helps you see your setup. You can find mailboxes or connectors that may need changes.
PowerShell
PowerShell gives you more control. It lets you check limits for many users or connectors at once. Use these commands in the Exchange Management Shell or remote PowerShell:
get-transportconfig | ft maxsendsize, maxreceivesize
get-receiveconnector | ft name, maxmessagesize
get-sendconnector | ft name, maxmessagesize
get-mailbox <username> | ft Name, Maxsendsize, maxreceivesize
Change <username> to the mailbox you want to check. These commands show the biggest send and receive sizes for your organization, connectors, and mailboxes.
Tip: You can check many mailboxes at once with
Get-Mailbox -ResultSize Unlimited | Select DisplayName, MaxSendSize, MaxReceiveSize.
Checking your settings helps you plan the best way to limit email size. This keeps your Exchange Server working well.
Limit Email Size Settings
Setting message size limits in Exchange Server helps you control email size. You can set these limits for the whole company, for connectors, or for each mailbox. Each level changes how emails move through your system.
Organization Level
At the organization level, you make the main rules for email size. These rules work for everyone unless you change them for certain users.
Default and Maximum Values:
Note: When you attach files, email servers make the message about one-third bigger. Set your limits a little higher than the file size you want to allow.
How to Set Organization-Level Message Size Limits
Using Exchange Admin Center (EAC):
Log in to the Exchange Admin Center.
Go to mail flow and pick receive connectors.
Click the More … button.
Choose Organization transport settings.
Change the Maximum receive message size (MB) and Maximum send message size (MB) to what you want, like 20 MB.
Click Save.
Wait a few hours for the changes, or restart Exchange services to make it work right away.
Using PowerShell:
Open Exchange Management Shell.
Type this command:
Set-TransportConfig -MaxReceiveSize 20MB -MaxSendSize 20MB
To make changes happen now, restart Exchange services:
Get-Service *Exchange* | Where-Object {$_.DisplayName -notlike "*Hyper-V*"} | Restart-Service -Force
Check your new settings:
Get-TransportConfig | ft MaxSendSize, MaxReceiveSize
If someone sends an email that is too big, Exchange will not let it go through. The sender gets a Non-Delivery Report (NDR) with an error like "552 5.3.4 Message size exceeds fixed maximum message size." This keeps your server working well and stops huge emails from causing trouble.
Connector Level
Connectors help emails move between your Exchange Server and other mail systems. You can set size limits for both send and receive connectors. This is good if you want to control email size for messages going to or coming from the internet.
Default and Maximum Values:
Tip: In Exchange Online, you cannot set connector-level limits. Use mailbox-level settings instead.
How to Set Connector-Level Message Size Limits
Using Exchange Admin Center (EAC):
Open the Exchange Admin Center.
Go to mail flow and pick send connectors or receive connectors.
Pick the connector you want to change.
Edit the Maximum message size.
Save your changes.
Using PowerShell:
For a send connector:
Set-SendConnector –Identity "Internet" –MaxMessageSize 25MB
For a receive connector:
Set-ReceiveConnector –Identity "MAIL1\Default MAIL1" –MaxMessageSize 25MB
If an email is too big for the connector, Exchange will block it. The sender gets a bounce-back message. This keeps your mail flow safe and stops big emails from slowing down your server.
Mailbox Level
You can also set email size limits for each mailbox. This is helpful if some people need to send or get bigger emails than others.
Default and Maximum Values:
Note: Messages sent between Microsoft 365 users can be up to 150 MB. But messages to the internet have extra overhead. Check your settings if you see delivery errors.
How to Set Mailbox-Level Message Size Limits
Using Exchange Admin Center (EAC):
Go to Recipients and pick Mailboxes.
Choose the mailbox you want to change.
Click Edit and go to Mailbox features.
Under Message size restrictions, set the Maximum send size and Maximum receive size.
Save your changes.
Using PowerShell:
To set limits for one mailbox:
Set-Mailbox -Identity "Debra Garcia" -MaxSendSize 25MB -MaxReceiveSize 35MB
To set limits for all mailboxes:
Get-Mailbox -ResultSize Unlimited | Set-Mailbox -MaxSendSize 25MB -MaxReceiveSize 35MB
If a user tries to send or get an email that is too big, Exchange will stop the message. The user gets an error message. This helps you control storage and keeps your system working well.
Remember: If you set email size limits too low, users may not send important files. If you set them too high, your server may slow down. Test your settings and change them if needed.
By setting the right limits at each level, you can limit email size for better performance and security. This also helps you avoid delivery problems and keeps your Exchange Server healthy.
Verify and Test
Confirm Settings
After you change message size limits, you should check if they work. You can use the Exchange Admin Center or PowerShell to do this.
To confirm settings in the Exchange Admin Center:
Log in to the Exchange Admin Center.
Click Recipients and then Mailboxes.
Choose a user’s mailbox.
Go to Mailflow settings and find Message size restrictions. Here, you can see the send and receive limits.
You can also look in mailbox properties. Go to the Mailbox tab and click Manage message size restriction.
If you want to check many mailboxes, select them all. Then look at Message size restriction under Mailflow.
It can take up to 30 minutes for new settings to start working on your Exchange Server.
To confirm settings with PowerShell:
Use these commands to check the limits:
get-transportconfig | ft maxsendsize, maxreceivesize
get-receiveconnector | ft name, maxmessagesize
get-sendconnector | ft name, maxmessagesize
get-mailbox <username> | ft Name, MaxSendSize, MaxReceiveSize
To see all mailboxes at once:
Get-Mailbox -ResultSize Unlimited | ft Name, MaxSendSize, MaxReceiveSize
For mailbox statistics:
Get-MailboxStatistics <user>
These steps help you make sure your Limit Email Size settings are working.
Send Test Email
You should test your new settings to see if they work.
Try sending an email just under the limit. It should send without problems.
Then, send an email that is too big. The system should block it and send you a Non-Delivery Report (NDR).
Ask someone else to send you a big email. This checks if the receive limit works.
If things do not work right away, wait a bit longer or restart Exchange services. Sometimes, changes need more time to start working.
Testing your settings helps you find problems early. This keeps your email system running well.
Best Practices
Recommended Limits
You should set message size limits that work well. Most companies let people get bigger emails than they can send. This lets users get large files but keeps outgoing emails smaller. The table below shows what limits are good for different systems:
Check your message size limits every few months. The STIG Viewer says to keep inbound message size at 10 MB or less for on-premises Exchange. Always pick limits that fit your company’s needs and storage space.
Monitoring
You need to check for email problems caused by message size limits. Exchange Server has tools like message tracking logs and message tracing. You can use PowerShell commands like Get-MessageTrackingLog for on-premises Exchange or Get-MessageTrace for Exchange Online. These tools help you see why emails fail and if the Limit Email Size setting is the reason.
Many companies use extra tools to watch email better. Here are some popular choices:
Tip: Site24x7 gives you alerts right away if emails do not get delivered. This helps you fix problems before users notice.
User Communication
You should always tell users when you change message size limits. Clear messages stop confusion and lower support questions. Try these steps:
Send an email to everyone before you change the limits.
Explain why you need to Limit Email Size and how it helps.
Give tips for sending big files, like using cloud storage or file-sharing.
Remind users what happens if they send emails that are too big.
Good communication helps users trust you and follow your email rules.
Setting the right email size limits helps your Exchange Server stay quick and steady. You keep things running well when you check and change these limits often.
You stop big emails before they cause trouble, which saves time.
Checking your system often helps you find problems early and keeps emails working.
Easy-to-read alerts and reports help users know about changes and not make mistakes.
Talking to users and watching your system stops storage problems and email delays. When you Limit Email Size, you help your company work better and follow the rules.
FAQ
What happens if you try to send an email that is too large?
You see an error message. Exchange blocks the email and sends you a Non-Delivery Report (NDR). The message explains that your email is too big for the server’s limit.
Can you set different size limits for different users?
Yes, you can. Use the Exchange Admin Center or PowerShell to set custom limits for each mailbox. This helps you give special users more or less space as needed.
How do you check if your new limits work?
Send a test email that is just under the limit. It should go through. Then, send one that is too big. You should get a bounce-back message. You can also check settings in the Admin Center or with PowerShell.
Do attachments count toward the email size limit?
Yes! Attachments add to the total message size. Encoding can make the email even bigger. Always check the final size before sending.