I have a couple of follow up questions on a topic that was discussed in July, 2003. Apparently MS Outlook may say that your message is 1 MB (for example) including attachments, but when you try to send the message it fails because it BECOMES larger than that during the SMTP process. 1. Is this true for all mail servers, or just Imail?
That is strictly an Outlook issue. Outlook generates the exact same E-mail no matter what mailserver is used.
2. Does this happen for HTML only or Rich Text and Plain text too?
It probably depends on the encoding that is used. Of course, Microsoft might say that the E-mail is 4 bytes ("test", which is all you wrote), when in fact it is 8K (because you used Microsoft Word to send the E-mail, without knowing that Word has *huge* overhead in an E-mail).
3. Can anyone expand upon Tripp's explanation below? What exactly happens and why?
Attachments (and sometimes message bodies) sent via E-mail are usually encoded. The 8-bit attachment needs to be converted to the 7-bit E-mail body. Doing so typically adds about 33% to the size of the E-mail.
4. What kind of expansion is typical? 10%, 50%?
Usually about 33% for binary attachments. Text or text-like attachments may add less; it's technically possible to add more than 33%, but that should be very rare (only with a poorly designed mail client).
For the curious, it's 33% because every 3 bytes of an attachment use up 4 bytes in the E-mail. 4/3 is 1.3333... There is a slight amount of overhead due to MIME headers, but it usually doesn't add much extra to the size of the E-mail. It would only be important when very small files were used.
5. When it was downloaded by the recipient, would it revert back to registering in Outlook as 1 MB?
Probably. If it only counts the actual size of the attachment (not the size of the E-mail) when sending, it probably does the same when receiving.
6. Does this only happen with MS Outlook?
I'm not aware of any other mail clients that give an inaccurate size for E-mails. :)
-Scott
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