Limiting factors for email file size

What are the limiting factors that control the size of an email that is being processed, not a campaign, but the individual email file size itself? I know that “max allowed packet” in mysql is one of these factors. We have set that value to 32MB. Does phpList use other factors?

For background, I have been working with two campaigns. For both I have attempted to send test emails to myself using the “Send test” functionality. They are not delivered. However, if I delete portions of the html code in order to reduce the file size of the email, the test will be delivered. I then attempted to run test campaigns using both versions and our subscriber test list. All email addresses in the test list, across multiple services (e.g. gmail, yahoo, hotmail) received the smaller sized email. Only one email address in the test list received the larger sized email.

phpList Advanced Statistics reports that all of the emails for both test campaigns were “Sent.”

The email size limitation is usually on the receiving end.
Telling us that one of the addresses received it helps point to the receiving mail server as being the problem.
If you have access to any of the receiving servers, you could check the email delivery reports and see if it was rejected.
If you have access to the server your sending from, you could do the same.
That’s where I would start.

Emails that are 32MB would take for a mail server forever to send. Isn’t there any way for you to reduce that size to something reasonable?
For me, reasonable is under 50KB.

Hi @NYChris,

Thanks for your reply. I hesitated to post this issue because the obvious answer would be that it is a limitation imposed by the receiving server. However, in this case the email that got through was received into a gmail account. There were others that were blocked that were also gmail accounts. So it would not appear to be an issue with the receiving server.

You indicate that we might be able to check the delivery reports to the receiving servers, if we have access to the receiving servers. Are the delivery reports for gmail, hotmail and yahoo mail generally available? If so, how would we access them?

The emails themselves are way below the threshold of 32MB. We only increased the max allowed packet variable in order to esnure that this was not a limiting factor. The actual size of the encoded html of the test email was about 27K. It included linked images, so if you tallied those up as well (which I don’t think you do in the size calculation) then the total email size is still under 360K.

Delivery reports are only available on servers you control.
If your server is running CPanel/WHM, you can access delivery reports through WHM>Email>Mail Delivery Reports
If the information indicates that it was an accepted and successful delivery, that means that your server delivered the email as it was intended. What the receiving server did with it is anybodies guess.
See the two attached screenshots for some CPanel/WHM clarity.

We are not currently running our own mail server so unfortunately that isn’t an option. However, due to the size of the emails, it is unlikely that the receiving server is setting a size limit anyway. Any other thoughts on why phpList (or other factors) might be restricting the delivery?

Do you have any error logs on the server?

Which server are you referring to?

The one that phplist is installed on.

The log from that batch indicates that all of the emails were “Sent” just like the Advanced Statistics page reported. However, 1 of the emails has an error during that batch with a (will retry later) designation. That was the only one that made it through.

There are no error logs for the “Send test” functionality that I know of.

I guess you would get bounces too? If the mails were rejected?

Better to make smaller emails. Why not link to a file for download?