Email Attachments

A2000 ONLINE SUPPORT DEPARTMENT

KNOWLEDGE BASE

DESCRIPTION:  My emails are hosted on A2000 server and failed to deliver attachment. Why?

1.  SERVER LIMITS

Our servers have the following limits for emailing file attachments (although, keep in mind the recipient's server may have different limits on what they will accept):

Technically, our Windows-based servers have a limit of 30 MB (which includes the email body and attachments) sent via SMTP and webmail, but that being said, in reality there are a number of factors that determine how large of a file attachment you may successfully send. These factors include:

• The fact that your attachment is MIME encoded, which causes the size to swell up to 40%.  So a 23 MB file on your hard drive will take up approx. 30 MB when MIME encoded.

• Any limits your email client has on attachments, which vary from email client to email client (for example Outlook 2010's limit is 20 MB).

• Any limits the recipient's server has on attachment size, which also vary from email service provider to email service provider (for example, Gmail, Yahoo! & Hotmail all have a 25 MB limit).

• Any limits the recipient's email client may have on attachment size.

How much free space is in the recipient's e-mail account, if their mailbox has a size limit. (If their mailbox is full, your message will be rejected.)

• How reliable your internal service provider (ISP) is at sending large files without corrupting them or aborting.

As you can see, there are many variables (factors) that can affect how large an attachment can be.  You may even encounter situations where you send an identical attachment to two people, and one receives it, and the other does not.  That is usually caused by one recipient's server rejecting the attachment for being too large, and the other one accepting it.

2.  TROUBLESHOOTING

When I send an e-mail with an attachment it is not delivered or bounces back why?

1. The most common reason is the size of the attachment. Please make sure the file you are trying to send is not to large. Typically an attachment 23 MB or smaller will go through.

2. The server is designed to block some attachment types if they are not zipped up. The two currently being blocked are: .src .exe. The reason for this is that your mailbox would be flooded every day with viruses if this was not in place. Unfortunately, there is no way to turn this off; your only option is to zip your attachment.

My webmail client says the limit is 30 MB but I cannot email this 30 MB file.

When you send an email attachment, it has to be MIME encoded so that it can be transmitted over the internet.  Unfortunately, this process adds about 40% to the size of the file during transmission. On the other end, it is unencoded and reverts back to the original size.  This means that a file that takes 30 MB on your hard drive becomes about 42 MB after being MIME encoded, which means it is too big to email.  

How can I send extremely large files?

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