Symptom:

Messages are being rejected based on size when they shouldn't be.

Mail is returned to sender with the following error:

The MMS SMTP Relay is returning your message because:
The message could not be delivered because the remote server returned the following error:
552 Requested mail action aborted: exceeded storage allocation - Maximum Message Size Exceeded

Details:

Base 64 encoding of Internet attachments can generate significant overhead. On average an encoded attachment is 25 to 50% larger then the original attachment. A 40% increase in size is not uncommon. For example, a message that includes nothing but a 2MB attachment might be as large as 3MB. What this means is that any MMS settings or policies that look for messages over a certain size may trigger on messages that you wouldn't expect them to. Quoted Printable encoding also has significant overhead associated with it.

Base 64 and Quoted Printable are Internet standards for encoding attachments. Microsoft Exchange server 5.5 and Outlook Express 5, normally use Base 64 for attachment encoding but can use Quoted Printable for some attachments.

To test this, open a new message in Outlook Express 5.0. Add an attachment of known size to the message. Save the message to the Drafts folder. (file->save) Drag the message from the Drafts folder and drop it onto the desktop. Right click the resulting .eml file and select properties. You will note that the file size is significantly larger then the original attachment.

You can also open the .eml file in notepad to view the headers to determine if the message was encoded Base 64 or Quoted Printable. Look for headers similar to the following:

Content-Type: image/jpeg;
name=mcrsftpic.jpg
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename=mcrsftpic.jpg

or

Content-Type: application/octet-stream;
name=2.pdf
Content-Transfer-Encoding: quoted-printable
Content-Disposition: attachment;
filename=2.pdf

Resolution:

This is not an issue with MMS, but a characteristic of the encoding standards that are used by the mail clients. The only current workaround is to allow for the overhead in you policies and SMTP Relay Set Up. For example, if your policies or settings don't allow mail over 5MB to be relayed, and a user is unable to send or receive a 4MB attachment, it may be necessary to increase your settings to allow messages that are 6MB to pass.

Additional Info:

http://support.microsoft.com/support/kb/articles/Q182/3/07.ASP

Original Author: DLANG
Original Submitter: ACUNY
Keywords: base64 base 64 quoted printable Maximum Message Size Exceeded tech tip attachment size MMS ID#22658