What is the maximum size of binary attachment in email?

  1. Using the WebMail system: Currently, the maximum size of binary attachment is limited to 10M bytes by the mail server. The total size of all attached files cannot exceed 10M bytes.
  2. Using other email clients (e.g. Outlook, Outlook Express): Currently, the maximum size of binary attachment is limited to 10M bytes by the mail server. The total size of all attached files cannot exceed 10M bytes.

Important Notes:

  1. It should be noted that other email systems may limit the incoming email size to a lower value e.g. 2M or 5M bytes which is usually set up by many ISPs. In other words, although mail sent out successfully, it may NOT be accepted by other email system.
  2. Since most email system also impose a quota system on email accounts, an email sent out may NOT be successfully accepted by the receiver's email system when the space of the receiver's email account left is NOT large enough to accept the incoming mail message.

Return to University In-house Email Service FAQ page

csc@cityu.edu.hk