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I have a program that will be sending a large output. I am just wondering what the max email attachment size is? According to RFC 1870 a mail server can reject messages because they are too large, but is there a max size when using SMTP/MIME? I can't find anything on this! The biggest I've heard people sending is 25mb.
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Open the Internet Information Services (IIS) 6.0 Manager. Select Properties. The SMTP Server Properties dialog is displayed. Select the Messages tab. In the Limit message size to (KB): field, enter the maximum message size.
Size Limits for Top Email Providers Gmail: 25 MB. However, the Gmail attachment size limit can be deceptive because Google encodes your email into a particular format before sending it. This process can double the size of your attachment; thus, the actual Gmail attachment size limit is closer to 12.5 MB.
If your file is greater than 25 MB, Gmail automatically adds a Google Drive link in the email instead of including it as an attachment. Learn more about Google Drive attachment sharing settings.
If you attach a file larger than 25 MB in size, it gets uploaded to Google Drive and Gmail places a download link to the file in the body of your email message. If you attach big files greater than 25 megabytes, the Gmail app uploads it to Google Drive and links to it instead of attaching it.
the relevant RFC is RFC 2821 (SMTP). Find it at http://www.ietf.org/rfc/rfc2821.txt .
See section "4.5.3.1 Size limits and minimums"
it says there (with targeted audience the implementers of the SMTP protocol):
message size restrictions should be avoided if at all possible
That doesn't mean that in practice such restrictions are not there as a result of implementation choices, or as a result of an intentional restriction through the configuration of that mail server.
Note, also, that attachments are (protocol-wise) just part of the message. These are coded in by e-mail clients.
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I have customer's that send out 100meg emails of GIS images. The only limitation is the size of the SMTP server imposes.
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Many mail servers impose a restriction on how large messages they will accept, but this is a per-server setting. You can find the limit if the server implements the ESMTP SIZE extension (most do). This is documented in detail in the RFC you are referring to.
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