What size restrictions are there on folder support in GMS?

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The release of Version 14.01 introduces support for large folders, including mailboxes, individual messages and message attachments. What if any restrictions remain on such sizes?


All of the GMS services have been updated to support large folders, messages and attachments throughout. The following restrictions will apply however:

  1. IMAP. The IMAP RFC expressly restricts message sizes to 4Gb. You will not be able to use IMAP to read messages above this size. Our IMAP server will in fact support large messages (thus technically breaking the RFC) but we have not found any IMAP clients that will support messages over this size.
  2. Outlook. Outlook is restricted to 2Gb messages. While we could change our Outlook plug-in to download large messages Outlook would be unable to store them. Similarly the Collaboration server does not support large messages (as Outlook is unable to).
  3. Webmail. GMS Webmail fully supports both large messages and large attachments. However Microsoft Internet Explorer does not. It is unable to download large attachments. We believe the limit is 2.7Gb. Both Firefox and Opera are quite happy with large attachment.
  4. POP. POP makes no restrictions on sizes so our server fully supports large messages. Client support is however unlikely at the present time.
  5. SMTP & POST. Neither of these services have any restrictions nd fully support the transmission of large messages. We are unable to comment on other server support.
  6. The only issue amongst all this is the handling of large messages when the IMAP client accessing the message does not support message sizes exceeding 4 Gb. By default a small message is returned to the client informing them of the presnce of a large message. This means that the client is able to manage and/or delete these messages without opening them in the client.

    While we would not recommend you change the large message settings from their default, if you have a particular requirement to handle messages greater than 4 Gb you may do so.

    If you are running an IMAP client that supports messages greater than 4 Gb in size please inform us.

    See Also:

    Keywords:large folder support

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