AKO Email Attachment Size and Types

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The official site can be found here https://www.us.army.mil/‎

Additional information about AKO Email can be found here.

Email/Attachment Size

Within the AKO/DKO webmail, the maximum email size is 5MB encoded.

Normally a file is 8 bit data; however, when send in an email it is base 64 encoded to make it printable ascii – this causes the file to be larger.  Base 64 encoding converts 3 uncoded bytes into 4 encoded ASCII characters.

What does this mean?  It means that a file that is approximately 3.7MB would become 5MB encoded.

Now if the email is signed or encrypted, that take up additional space within the email and reduce the size of the file that can be attached.  Normally to get the email to 5MB encoded, signed, and encrypted, the attachment would have to be approximately 2.6MB and no message text to make it through the AKO/DKO webmail

Summary

Largest an attachment can be in an unencrypted or unsigned email is about 3.7MB.
Largest an attachment can be in an encrypted and signed email is about 2.6MB

Work Around

Some ways around the email size limit are:

By setting up your AKO/DKO webmail to an external email client such as Outlook or Thunderbird, you can send a message that is as big as 20MB.
Uploading the file to an AKO/DKO folder and giving the user access to the file.  Then you can send a link to the file.  This will only work if the user’s that you are sending to has access to the AKO/DKO portal.  If not, then you will want to use the option above to send an email that is larger than 5MB.

Attachment Types

In order to comply with NETCOM guidance 2004-11A certain attachment types are no longer allowed through the AKO/DKO mail system:

.ace, .ad, .ade, .adp, .asp, .b64, .bas, .bat, .bat., .bhx, .ce0, .ceo, .chm, .cmd, .com, .com., .cpl, .crt, .dbx, .dll, .doc.bat, .doc.com, .doc.pif, .dot, .eml, .exe, .exe., .hlp, .hqx, .hta, .inf, .ins, .js, .jse, .lnk, .mdb, .mde, .mim, .msi, .msp, .nch, .ocx, .pi, .pif, .rar, .reg, .scr, .sct, .shb, .shs, .txt.scr, .upx, .url, .uu, .uue, .vbe, .vbs, .vss, .vst, .vsw, .wmi, .ws, .wsc, .wsf, .wsh, .xxe, .zip

These attachments are blocked to prevent email based viruses from spreading. One way to send an email with one of the above attachment types is to:

Upload the file to an AKO/DKO folder and give the user access to the file.  Then you can send a link to the file.  This will only work if the user’s that you are sending to has access to the AKO/DKO portal.  If not, then you will want to use the option above to send an email that is larger than 5MB.

If you send attachments with a space in the file name, some anti-virus scanners will not be able to scan the attachment which can cause a delay in delivery or the message being returned to you as undeliverable.

HTML Attachments

In response to JTF-GNO and Army directives, AKO/DKO

no longer accepts unsigned email containing html attachments and is replacing the html attachment with a text attachment that says “This message contained an html attachment that has been removed by AKO/DKO in response to JTF-GNO and Army directives.”

Remember, The Army’s Enterprise Email is now officially released and the above information may not be accurate. For more information regarding Enterprise Email click on the link above.