Question about how email send of attachments works

highstream said:

Once a week I complete and email an Excel worksheet file as an attachment from my email program, Sylpheed. The email provider is Fastmail. Most times, anywhere from maybe 15 or 30 seconds to several minutes after the send completes, within the email program I remove the attachment from the Send entry, so as to minimize file storage. The past couple of weeks, the Excel worksheet file has arrived uncompleted. Checking back, the sent file is completed, which makes me wonder, Is there something about the way email works, the timing of when I remove the attachment, that could be involved in this? Win 10/21H2. Thanks,

not sure how the timing works , but wouldn't it be easier to just delete the send attachments after a day at least ?

Unfortunately sending messages with attachments relies upon the computer's cache [temporary storage] having the full data then sending doesn't get completed. The mail server can only send what it receives so it is best to wait at least a few minutes to be sure it has time to send. I use Webmail which is on my ISP's server or my Domain, quicker. A lot of variables exist such as speed of the Internet connection, speed of the connection computer to Router/Modem, how far it has to go/number of servers it goes through. In a Command Prompt put in tracert plus the address of the destination to see more, e.g. tracert tenforums.com.

Maybe I've posed this wrong, because there's still a puzzle: the Excel file is getting to the other end but without the information I've added (and saved). So if I remove the attachment from the email in the Sent folder, is cache drawing on a previous, apparently uncompleted copy? And why would what's in the Send folder matter?

A lot depends upon the size of the attachment, larger ones take longer to transfer and if deleted too soon will be incomplete.

The Sent folder holds the messages as a type of backup, if no longer needed can be deleted. I use Outlook.com but haven't used Microsoft Outlook for quite some time but the older versions did have a feature to set for sending at a later time such at the end of the business day or could be set to send immediately, maybe after checking for new mail.

Next time to send, wait a few minutes then check with the recipient. A test could be done by sending a BCC [Blind Copy] to yourself at same address or a second address you have to verify the problem is or is not on the recipient's end.