SMTP size limit

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  • djn
    Senior Member
    • Mar 2004
    • 140

    SMTP size limit

    Hello all.
    One of my customers is a printing shop and needs often to send large (5-40 MB) files as e-mail attachments. Since the move to the new server such emails start more or less at a decent pace and then crawl down slower and slower until the connection fails.
    Is there a limit somewhere on the smtp server regarding attachment/message size?
  • AndrewT
    Administrator
    • Mar 2004
    • 3653

    #2
    Originally posted by djn
    Hello all.
    Is there a limit somewhere on the smtp server regarding attachment/message size?
    No. But large e-mail attachments aren't exactly reliable (40MB).

    Comment

    • cathode
      Member
      • Oct 2004
      • 88

      #3
      I have never had any luck sending attachments over about 2MB. At around 2mb I get an error saying the message could not be sent or something to that effect, but the message goes thru. Anything larger from there, and it just fails. Think this could be timeout settings or something in my email program?

      Comment

      • AndrewT
        Administrator
        • Mar 2004
        • 3653

        #4
        Could be. Sending large e-mail attachments does require a rather reliable connection. I know I've sent several hundred MB through the same cPanel mail server setup with no problems. But its easy for it to fail as the size increases.

        Comment

        • djn
          Senior Member
          • Mar 2004
          • 140

          #5
          Thank you. I was just double-checking, as those sending troubles appeared first somewhere last week. More, I tried the same setting up their mail client to use my Gmail account as smtp and it was briskly sending out the stuff up to gmail's own size limit of 20 MB ca. I'm going to try out their broadband connection with another PC as soon as I can borrow one...
          What are you folks using to check ISP connection quality? Thanks for any idea.

          Comment

          • AndrewT
            Administrator
            • Mar 2004
            • 3653

            #6
            Any lost packets can quickly lead to a time out. Mail is particularly sensitive about this. You could just run a really long ping sequence to the mail server while you're sending the attachment.

            Comment

            • djn
              Senior Member
              • Mar 2004
              • 140

              #7
              Good idea. A quick and dirty batch file with a loop and a 15 sec timeout should do the job.

              Comment

              • djn
                Senior Member
                • Mar 2004
                • 140

                #8
                Hello. Has something changed lately regarding the message size limit?
                I've just seen a Thunderbird replying something about a global size limit on the server side, somewhere around 52 MB.

                Comment

                • AndrewT
                  Administrator
                  • Mar 2004
                  • 3653

                  #9
                  Nothing has changed in this regard. Though I can't say I would recommend sending attachments that large. You do have to keep in mind the quotas of the domain and email account itself.

                  Comment

                  • Frank Hagan
                    Senior Member
                    • Mar 2004
                    • 724

                    #10
                    Since this thread started, there are alternatives like Dropbox that should probably be used for large attachments. The customer gets a link and retrieves it. Less chance of it hitting the recipient's max mailbox threshold. I read a few days ago that Hotmail increased the size of attachments to 40 or 50 GB, but Gmail is still at 20 GB.

                    Comment

                    • djn
                      Senior Member
                      • Mar 2004
                      • 140

                      #11
                      I agree, sending such amount of stuff by mail is definitely not a best practice. It all started when my client first received that 52 MB PDF attachment by mail and tried to send it along to another recipient. I explained them that the file is twice the attachment size limit for Gmail and not a very polite thing to drop into a recipient's mailbox anyway, and they've agreed.
                      I was curious about the error message, as Thunderbird's messages are usually pretty reliable about what's going on. That message said explicitly that it was the server making a fuss about the overall size, thus my question...

                      Comment

                      • AndrewT
                        Administrator
                        • Mar 2004
                        • 3653

                        #12
                        Nothing has changed concerning attachments. Limiting factors will continue to be the domain and email account's disk quota.

                        Comment

                        • AndrewT
                          Administrator
                          • Mar 2004
                          • 3653

                          #13
                          Out of curiosity I took a quick look at the Exim docs and did find that the default message_size_limit (when the value is unset as it is on our servers) is 50MB. I think you're the first person to have reported even hitting this limit. IMHO it is a very fair and generous limit.

                          Comment

                          • djn
                            Senior Member
                            • Mar 2004
                            • 140

                            #14
                            Hey, it's nice once in a while to be a 'first'
                            This doesn't happen all that often.

                            Comment

                            • djn
                              Senior Member
                              • Mar 2004
                              • 140

                              #15
                              FWIW, I agree: 50 MB is way over what any sensible attachment should need. I'd hate one such elephant landing in my mailbox.

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