Select Page

How to fix email error 552 – ‘5.3.4 Message size exceeds fixed maximum message size’ in Exchange servers

How to fix email error 552 – ‘5.3.4 Message size exceeds fixed maximum message size’ in Exchange servers

Users sending messages with attachments to recipients hosted in Exchange servers can end up receiving bounce mails due these attachments.

Our Hosting Support Engineers support hundreds of Exchange servers for web hosts, web designers and other online businesses.

In these servers, we’ve seen huge attachments or unsupported attachments formats causing email error 552.

The error message seen by the senders in the bounce mail in cases of huge attachment size limit would be error 552 – ‘5.3.4 Message size exceeds fixed maximum message size’.

If the bounce happens due to the content of the attachment, the error message would be similar to error 552 – ‘5.7.0 Our system detected an illegal attachment on your message.’


What is email error 552 ‘5.3.4 Message size exceeds fixed maximum message size’

Every mail server has custom settings for the size of mails users can send and receive through it. These limits can either be global or individual-account specific or both.

To limit bandwidth usage, this email size limit is often restricted to a few MBs in most servers. If the email size exceeds that limit, it will be rejected by the mail server.

Error 552 ‘5.3.4 Message size exceeds fixed maximum message size’ is an email error commonly seen in bounce messages that generate from recipients using Exchange mail server.

In an Exchange server, there are mainly 4 settings for message size limitations:

a. Global value for the mail server
b. Receive and Send Connectors setting
c. SMTP Virtual Server setting
d. Individual user mailbox restriction

If the message size in the email exceeds any of these limits that are allowed for a particular email user account, it will be rejected with this error 552 message.



To resolve a valid email bouncing with error 552, these attachment limits have to be increased or adjusted appropriately.

But before we get into the detailed steps on how to increase these limits to accept valid user mails with attachments, we’ll see how these message size limits are to be calculated.

[ Worry no more about web or mail errors. Get an experienced server admin to manage your servers for as low as $12.99/hour. ]


How to determine the email message size limits?

In Exchange mail servers, content conversion happens for mails. Exchange server converts an internet/MIME message to MAPI/Exchange format, and vice versa for transmission.

After this content conversion process, the message size generally increases by about 30%. As a result, a message of 9 MB may fail to deliver to a server with size limit 10 MB.

Also, the precedence of the message size limits has to be noted before changing the settings. The maximum allowable message size for a server should be set as the organizational limit.

If the message is sent to or received to the server from a user on the Internet, this organizational limit will be applied to that mail.

But for internal users who send mail to each other after successful authentication, the user mailbox limit takes precedence over all other size restrictions.

So, for a server to accept messages from the internet with size around 15 MB, all the message limits should be set at 20 MB, considering the content conversion size.



Never again lose customers to poor server speed! Let us help you.

Our server experts will monitor & maintain your server 24/7 so that it remains lightning fast and secure.


Submit a Comment

Your email address will not be published. Required fields are marked *

Bobcares is a server management company that helps businesses deliver uninterrupted and secure online services. Our engineers manage close to 51,500 servers that include virtualized servers, cloud infrastructure, physical server clusters, and more.