Solved Issue Sending PDF Attachment (9MB)

[maxb1999]

Hi,

I'm not sure if this should be posted on the Roundcube forum or here, so I'll keep it short.

A customer is unable to send an email with a PDF attachment of approximately 9MB. I checked the settings, and the maximum allowed size should be 20MB.

I tested sending other PDFs (5.9MB and 5.3MB), and those were sent successfully. I initially suspected a corrupt file, but another 9MB PDF worked fine.

Since disk space was almost full, I temporarily added 5GB and retried sending the PDF, but the issue persists.

Do you have any idea what might be causing this?

 

[ericosman]

Does your server give an error or the receiving one?

 

[maxb1999]

Does your server give an error or the receiving one?

I got an error from a Gmail and an Outlook address. Here are the error messages stating that the file exceeds the allowed size.

G-mail

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

[email protected]
host 37.97.133.147 [37.97.133.147]
SMTP error from remote mail server after pipelined MAIL FROM:<[email protected]> SIZE=12924495:
552 5.3.4 Message size exceeds fixed limit
Reporting-MTA: dns; server7.ersitehosting.com

Action: failed
Final-Recipient: rfc822;[email protected]
Status: 5.0.0
Remote-MTA: dns; 37.97.133.147
Diagnostic-Code: smtp; 552 5.3.4 Message size exceeds fixed limit
Return-path: <[email protected]>
Received: from localhost ([127.0.0.1] helo=server7.ersitehosting.com)
by server7.ersitehosting.com with esmtpa (Exim 4.98)
(envelope-from <[email protected]>)
id 1tg3Wk-0000000EHSL-1MmO
for [email protected];
Thu, 06 Feb 2025 16:10:50 +0100
MIME-Version: 1.0
Date: Thu, 06 Feb 2025 16:10:50 +0100
From: [email protected]
To: Max <[email protected]>
Subject: test
Message-ID: <[email protected]>
X-Sender: [email protected]
Content-Type: multipart/mixed;
boundary="=_b0920f804753a6f808053dadb3e8b1ad"
X-Exim-DSN-Information: Due to administrative limits only headers are returned

Outlook

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

[email protected]
host 37.97.133.147 [37.97.133.147]
SMTP error from remote mail server after pipelined MAIL FROM:<[email protected]> SIZE=12924620:
552 5.3.4 Message size exceeds fixed limit
Reporting-MTA: dns; server7.ersitehosting.com

Action: failed
Final-Recipient: rfc822;[email protected]
Status: 5.0.0
Remote-MTA: dns; 37.97.133.147
Diagnostic-Code: smtp; 552 5.3.4 Message size exceeds fixed limit
Return-path: <[email protected]>
Received: from localhost ([127.0.0.1] helo=server7.ersitehosting.com)
by server7.ersitehosting.com with esmtpa (Exim 4.98)
(envelope-from <[email protected]>)
id 1tg3C4-0000000E9L7-24Lf
for [email protected];
Thu, 06 Feb 2025 15:49:28 +0100
MIME-Version: 1.0
Date: Thu, 06 Feb 2025 15:49:28 +0100
From:[email protected]
To: [email protected]
Subject: test
Message-ID: <[email protected]>
X-Sender:[email protected]
Content-Type: multipart/mixed;
boundary="=_2dd134e2db8a12c579e0710a1d2aae71"
X-Exim-DSN-Information: Due to administrative limits only headers are returned

 

[maxb1999]

I think the problem is with the Gmail or outlook. Sending form a Rouncube to a Roundcube address work perfectly.

 

[Richard G]

I don't think so.
It's not gmail or hotmail reporting the error but the remote MTA and that's your backup mailserver.

host 37.97.133.147 [37.97.133.147]
SMTP error from remote mail server after pipelined MAIL FROM:<[email protected]> SIZE=12924620:
552 5.3.4 Message size exceeds fixed limit
Reporting-MTA: dns; server7.ersitehosting.com

Then a little further:

Final-Recipient: rfc822;m[email protected]
Status: 5.0.0
Remote-MTA: dns; 37.97.133.147

So the remote-mta which is refusing the mail is this server.
And this resolves to your backup server, while it's send from your server7.

Then you can see the attachment is not 9 but 12 MB. I would check on the backup server if there a bigger transfer is allowed.

Or I must be missing something, but I don't see any hotmail or gmail responses in the headers.

P.s. I would mask the correct hotmail e-mail address in your mail, like I did.

 

[maxb1999]

I don't think so.
It's not gmail or hotmail reporting the error but the remote MTA and that's your backup mailserver.



Then a little further:

So the remote-mta which is refusing the mail is this server.
And this resolves to your backup server, while it's send from your server7.

Then you can see the attachment is not 9 but 12 MB. I would check on the backup server if there a bigger transfer is allowed.

Or I must be missing something, but I don't see any hotmail or gmail responses in the headers.

P.s. I would mask the correct hotmail e-mail address in your mail, like I did.

Thank you for your message and the tip about masking the mail address.

I’ll submit a ticket to the company that provides our server to be sure. The only thing I find confusing is that when I send the PDF from [email protected] to [email protected], it works fine.

When I receive an answer from the company, I will provide more information.

 

[maxb1999]

Thank you for your message and the tip about masking the mail address.

I’ll submit a ticket to the company that provides our server to be sure. The only thing I find confusing is that when I send the PDF from [email protected] to [email protected], it works fine.

When I receive an answer from the company, I will provide more information.

The issue was indeed with the backup mail server, which had a message size limit of 10MB. While Roundcube and PHP allowed larger attachments, the SMTP server rejected emails exceeding this limit.

This explains why sending emails within the same domain (@tremonte.nl to @tremonte.nl) worked fine—those emails never left the primary mail server.

The hosting provider has now increased the message size limit to 20MB, and larger attachments can be sent successfully.

 

[Richard G]

The issue was indeed with the backup mail server,

It almost couldn't have been anything else.
Tip: Always check which server is sending and which server is reporting the error, that always sheds a light on exactly who is refusing the mail.

Anyway, glad to read it's working again.