Set Maximum Email Message Size for Outbound and Inbound messages

To prevent abuse of the mail server and encourage better interoperability with other mail servers, administrators may define the maximum size of email a user can send or receive. System administrators manage incoming size limits for the server as a whole. Outgoing size limits can be set for all domains using Domain Defaults or managed on a domain-by-domain basis, as needed.

When setting the maximum message size, keep in mind that when a message is sent, mail servers automatically MIME encode the message, which will increase its size roughly 35-40%. If you would like your users to be able to send 10 MB messages, you should make the max message size 15 MB.

This article applies to recent versions of SmarterMail. View articles for SmarterMail 15.x and earlier.

Incoming Size Limit
At the system level, setting the max message size will reject all incoming messages that exceed the defined value. Follow these steps to set the maximum email size for inbound messages in SmarterMail:

  1. Log in as the system administrator.
  2. Click the Settings icon.
  3. When the Settings page loads, click Protocols in the navigation pane.
  4. Scroll to, or locate, the SMTP In card.
  5. In the Max Message Size field, type the maximum size, in Kilobytes, incoming messages can be. If you don't want to limit incoming message size, type in 0.
  6. Click Save.

Outgoing Size Limit
At the domain level, setting the max message size will limit the size of email a user can send outbound. Follow these steps to set the maximum attachment size message that a user can send.

To set up Domain Defaults:

  1. Click the Manage icon.
  2. Click the Actions (...) button. 
  3. From the dropdown menu, select Domain Defaults.
  4. On the Limits card, find Max Message Size KB. Type in a number to correspond to the maximum number of Kilobytes for a message that's sent. (E.g., 4000KB roughly equals 4MB.) If you don't want to limit the outgoing message size, type in 0.
  5. Click the Save button.
  6. Once you've modified this setting, you will want to propagate the change to all domains on the server.
  7. To do this, click the Propagation button.
  8. A modal window will open, where you can select the setting(s) you want to propagate. 
  9. Once finished making your selection(s), click the Propagate button.
To modify settings for a single domain:
  1. Select the desired domain from the list of domains in the content pane.
  2. The domain's settings will open.
  3. Find the Limits card.
  4. In the Max Message Size field, type the maximum size, in Kilobytes, for all outgoing messages for users on that domain.
  5. Click Save.
 
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It is not clear whether this setting is for total message size. I had this setting at 30MB, but the user could still not send messages out that had attachment size of 10MB. I am not clear if there is a separate setting for attachments (even though attachment is briefly mentioned here, for outgoing, version 13.x), or perhaps there are individual limits set per user.
David Alexander (May 1, 2015 at 4:31 PM)

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