A non-delivery report is received. Print Messages from mail servers - what do they mean? Postfix email size limit

Quite often, in the course of work, corporate users need to send large attachments through an email client, and they may face an error sending a letter.

Outlook

The thing is that in the Outlook mail client (including versions 2010/2013/2016) there is limit on the maximum size of an attachment to the letter - 20 MB. Moreover, it does not matter whether one large file is attached to the letter or several small ones - the limit on the total size of attachments will always be 20 MB.

When trying to send an email larger than 20 MB in Outlook, an error window appears - The attachment size exceeds the allowable (attachment size exceeds the allowed limit):

In the event that your mail server and the recipient's server support a larger size of mail messages, you can increase the attachment size limit in Outlook.

You can change the maximum attachment size limit in Outlook only through the registry; there is no such setting in the Outlook GUI.

Procedure

After the changes have been made, you can attach an attachment larger than 20 MB to the letter in Outlook (in our example, we attached a 58 MB pst file to the letter).

In the event that your mail server or the sender's server does not support large letters, when you send a large letter, you will receive an NDR-Non delivery report, which will indicate that the maximum message size has been exceeded. Below are the popular options for the text of such a bumper:

• Attachment size exceeds the allowable limit
• 552: Message size exceeds maximum permitted
• System Undeliverable, message size exceeds outgoing message size limit
• The message was not sent; reduce the message size and try again

MS Exchange

In Exchange, you can change the allowed letter size at three different levels:

• In the transport settings of the Exchange organization
• In the parameters of the sending / receiving connectors
• In the settings of a specific user's mailbox

The current limits can be viewed through the Exchange Management Console (EMC), but it's much easier and faster to use PowerShell. In the Exchange Management Shell console, or after connecting to Office 365 via a remote PowerShell session, run the commands:

Get-transportconfig | ft maxsendsize, maxreceivesize get-receiveconnector | ft name, maxmessagesize get-sendconnector | ft name, maxmessagesize get-mailbox administrator | ft Name, Maxsendsize, maxreceivesize

The commands should return something like the following, containing the current limit settings:

• In the transport parameters of the entire organization, the size indicates that the received / sent message should not be more than 25 MB
• All connectors have a 10 mb limit
• For the administrator mailbox, the limit on the size of letters is not set (unlimited)

Naturally, the last command checks the limits for only one mailbox. You can deduce the limits on the size of letters for all users of the organization as follows:

Get-mailbox | ft Name, Maxsendsize, maxreceivesize

To increase the maximum message size (both received and sent) accepted by the Exchange Transport service from 25 MB to 100 MB, run the command:

Set-TransportConfig -MaxSendSize 100MB -MaxReceiveSize 100MB

The syntax of the command for changing the limit on the size of letters for connectors is the same, but the change command will have to be executed for each connector.

Set-SendConnector "Connector1" - MaxMessageSize 100Mb Set-ReceiveConnector "DefaultConnector1" -MaxmessageSize 100MB

Or for all connectors:

Get-SendConnector | Set-SendConnector -MaxmessageSize 100MB Get-ReceiveConnector | Set-ReceiveConnector -MaxmessageSize 100MB

Similarly, you can change the limit for all mailboxes in the organization:

Get-Mailbox | Set-Mailbox -MaxSendSize 100MB -MaxReceiveSize 100MB

Limits set in this way limit the maximum message size, regardless of whether it contains an attachment or not.

Using the web interface

There is another option - through the web interface. Open the Exchange admin center and go to the section mail flow -\u003e send connectors -\u003e organization transport options:

and set the required maximum investment. Please note that when sending to an external server, the attachment is encoded in MIME64 format, which increases the total volume of the letter by about 30%.

We are also ready to assist in any MS Exchange settings.

We offer our clients implementation of this project and subsequent IT maintenance within the framework of IT outsourcing.

An alternative option is to rent a pre-configured Exchange server with maintenance or connect to a public cloud Exchange based on the EFSOL structure.

If you received an email from Mailer-Daemon with the subject "Undelivered Mail Returned to Sender", then the sent email was not delivered to one or more recipients. The reason why the original email was not delivered is listed at the end of the notification at english language... The most common reasons are listed below.

Invalid recipient address

User not found
User unknown
No such user here
Unrouteable address
Invalid mailbox
Mailbox unavailable

This error may mean that you are trying to send a letter to a non-existent address. Check the recipient's address and try again.

Sample error message:
: host mail.example.com said: 550 5.1.1
: Recipient address rejected: User unknown in local
recipient table (in reply to RCPT TO command)

There is no free space in the recipient's mailbox

The error message contains the lines:
account is full
Quota exceeded
User has exhausted allowed storage space
error writing message: Disk quota exceeded

The message size is larger than the limit on the recipient's server

The recipient's server has a limit on the maximum message size. If you are sending multiple files, try sending them in several different emails.

Example:
message size 7520647 exceeds size limit 6000000 of server mail.example.com

This means that a 7.5 megabyte letter was sent, and the recipient's server accepts letters no more than 6 megabytes in size.

Recipient's server does not accept mail

The error message contains the line:
Operation timed out

The recipient server is down. Perhaps you made a mistake in the recipient's address and the letter was sent to the wrong server. If the address was specified correctly, then try to contact the addressee using a different address.

A non-delivery report is a message sent by the mail server to the sender when the recipient's mailbox is unavailable, does not exist, or the sender / recipient's server reports an error, due to which it cannot deliver the letter to the addressee within the allotted time.

The text of the letter contains the text of the error, the address of the mailbox, the error code and the reason why this letter could not be delivered.

For details on error codes, see RFC 3463.

We will provide examples of the most common error messages when messages are not delivered.

# Error: No such user (User not found / No correct recipients / Bad recipient address syntax / Bad address mailbox syntax)

the error indicates that the recipient's mailbox does not exist on the remote server. Check that the recipient's address does not contain extra characters, spaces, or symbols. Check the address with the recipient again or try to contact recipients using alternative methods.

# Error: Message rejected under suspicion of SPAM

If the report contains the line "Message rejected under suspicion of SPAM", the content of your message has been recognized as spam. Contact the support service of the server that rejected your letter to find out the reasons for the problem.

If only spam comes from your mailbox, then some mail servers block receiving letters from it for 24 hours. In this case, the NDR will contain the string "Client host [ ] blocked using spamsource ..; see ... "or" Blocked by spam statistics - see ... ".

If you are sure that your computer is not infected with a virus and that no spam has been sent from it, notify the support service of the server to which the letter was sent via the form feedbackby attaching a file with a report to the letter.

# Error: 550 spam message discarded / rejected

Your message was blocked by the anti-spam filter system. To solve this problem, you need to temporarily stop the mailing and make the necessary settings in accordance with.

# Error: 550 relay not permitted

There may be several reasons for this error:

Authentication when sending is not enabled in the mail client settings;

MX servers have incorrect values \u200b\u200bor for other reasons that can be clarified with the owners of the mx servers.

# Error: Connection timed out / C onnection refused / retry time not reached for any host

T these errors usually result fromtechnical problems on the recipient's mail server. Try to wait a while and try again, or contact the recipient using alternative methods.

# Error: Mailbox Full or User quota exceeded / Mailbox size exceeded

This problem occurs because the recipient's mailbox is full. Try to wait a while and try again, or contact the recipient using alternative methods.

# Error: Access to this account (user) box_name is disabled or Mailbox is disabled

This error is generated because the recipient's mailbox has been deleted or blocked for non-use. Try to contact the recipient using alternative means.

# Error: 550 Access from ip address blocked

Most likely your IP address is on one of the blacklists. In this case, contact us at technical support for a consultation.

# Mistake contains the code "0x800CCC"

To solve this problem, try changing the SMTP port from 25 to port 2525 or 587 in the settings of your mail program.

If all this does not help, then try using your ISP's SMTP server for sending.

# Error: Message infected by virus

If the error "Message infected by virus" is indicated in the report, it means that your message has been marked by the recipient's mail server as infected with a virus.

If the report contains the error “The recipient has exceeded their message rate limit. Try again later ”, the delivery of letters to the recipient's address was temporarily suspended due to the large number of letters arriving in his mailbox per unit of time. Try to resend the email after 6 hours.

# Error: Message size exceeds fixed limit (Error: message file too big)

If the report contains the line "Error: message file too big" or "Message size exceeds fixed limit", the attachment that you send in the message cannot be accepted by the mail server due to the restrictions set on it.

The maximum size of emails with attachments should not exceed 10 MB.

# Error: too many connections

If the error "Error: too many connections" appears when sending a message, your mail server creates a large number of calls to a third-party mail server per unit of time, which leads to an increase in the load and slowdowns in work. Try to contact the administration of your mail service an alternative way to contact and report the problem.

# Error: too many recipients

If the error "Error: too many recipients" appears when sending a message, your message has too many recipients: more than 100 addresses in the fields To whom, Copy and Hidden copy... Please edit the recipient list and try again.

Prerequisite: The mail server is implemented on the postfix + dovecot + roundcube bundle. The roundcube web interface in the Add Attachment pop-up window indicates: Maximum file size 2 MB. Accordingly, larger files are not attached.

Note: postfix defines restrictions not investments, and total letters. In the default configuration, the default email size limit was 10MB. Therefore Roundcube, displaying a message about the maximum size of 2MB, is in no way guided by the postfix configuration. As a php application, Roundcube focuses on the php server configuration. However, it must be remembered that the size of the letter consists not only of the attachment, but also of the text of the letter and the service code. Therefore it is necessary to set a higher value acceptable size letters than the size of the allowable attachment size.

1. To the configuration file /etc/postfix/main.cf, it is necessary to enter a parameter that determines the maximum allowable message size, since it is absent in the default configuration. For example, set the maximum allowable size of a mail message to 25 MB.

# postconf -e message_size_limit \u003d 25600000

# postfix reload

It is necessary to make sure that the message size does not exceed the maximum allowable size of the user's mailbox.

# postconf -d - displays the default server settings

mailbox_size_limit \u003d 51200000

message_size_limit \u003d 25600000

virtual_mailbox_limit \u003d 51200000

From the listing you can see that with the maximum mailbox size of 50MB, we increased the email size to 25MB. This box won't last long. In this case, it is advisable to increase the size of the box, for example, up to 200MB.

Again, when viewing the configuration file, we will not find the mailbox_size_limit and virtual_mailbox_limit parameters, so we add them:

# postconf -e mailbox_size_limit \u003d 204800000

# postconf -e virtual_mailbox_limi \u003d 204800000

# service postfix restart

Checking the actual values:

# postconf -n mailbox_size_limit
mailbox_size_limit \u003d 204800000
# postconf -n virtual_mailbox_limit
virtual_mailbox_limit \u003d 204800000
# postconf -n message_size_limit
message_size_limit \u003d 25600000
#

2 ... All of the above manipulations are pointless until we allow php to work with files of this size.

The maximum file size that can be uploaded using a php script is defined in the file /etc/php.ini

; Maximum size of POST data that PHP will accept.

post_max_size \u003d 16M

; Maximum allowed size for uploaded files.

upload_max_filesize \u003d 16M

; Maximum amount of memory a script may consume

memory_limit \u003d 64M

After editing php.ini, you need to restart apache

#service httpd restart

3. If the roundcube user session has been open all this time, then you need to re-authorize.