The following files couldn't be attached: file name. Please try again later.

Hi. I'm Brian and I'll try to help.

This forum is dedicated to problems using classic Outlook for Windows. You mention working with Edge and Chrome. Classic Outlook doesn't access the mailbox using a web browser so I suspect you're actually referring to Outlook online at https://outlook.office.com/ or https://outlook.live.com/ . That's covered in a different forum.

How are you trying to attach the file? Are you opening the new message window and then using the paper clip icon to try to attach the file? If so, the first thing I'd check is my OneDrive storage by visiting https://outlook.live.com/mail/0/options/general/storage to see the "Microsoft storage" and "Email storage" values. Are both of those values sugniuficantly below their maximum allowed values?

Hello Brian and my fellow weary travelers simply trying to send an email with an attachment,

I am not B.Rich, but I had the same problem. Using the Outlook web app, getting the same error. I usually try to attach files by simply dragging them onto the email, but selecting the paper clip and picking a specific file to attach also didn't work. Storage values were well below their limits. The file was a .png and is roughly 200kb similar to the original post. Other file types also did not attach. As per this post on the same issue I tried disabling my firewall and attaching the file to no avail. Clearing my cookies and using light mode as suggested here did not fix it. Using Firefox vs Chrome does not fix it. Restarting my computer did not fix it.

For whatever god forsaken reason, deleting the draft and re-composing the email was what fixed the issue.

HOWEVER. This was not the end of my woes, for you see while I was now able to attach the image to the email upon sending it I was greeted with an Undeliverable message. Despair. Upon further inspection the reason stated was that the message was larger than the size limit for messages. But how could this be when the attachment was so small? In one last desperate attempt to finally send this god damn email after over an hour of trying to figure this **** out I decided to delete all the previous messages in the email chain. It was fairly long after all, and was the only thing I could think of to reduce the 'message size'. Fortunately this worked, and I was finally able to send the email. I do not know if these two issues are related, and I would not be surprised if they were.

Here is some information from the Undeliverable email. Arcane wizardry that is beyond me, but perhaps can be useful to someone on the outlook team to prevent this from ever happening again

Generating server: TYCP286MB0718.JPNP286.PROD.OUTLOOK.COM
Remote server returned '554-5.3.4 Content conversion limit(s) exceeded 554 5.3.4 STOREDRV.Submit.Exception:ConversionFailedException; Failed to process message due to a permanent exception with message [BeginDiagnosticData]Content conversion: Maximum number of body parts (250) per message exceeded ConversionFailedException: Content conversion: Maximum number of body parts (250) per message exceeded[EndDiagnosticData]'

Original message headers:

Received: from TYCP286MB0718.JPNP286.PROD.OUTLOOK.COM
 ([fe80::c127:3d3f:87a0:a9fb]) by TYCP286MB0718.JPNP286.PROD.OUTLOOK.COM
 ([fe80::c127:3d3f:87a0:a9fb%7]) with mapi id 15.20.7386.017; Thu, 14 Mar 2024
 01:47:11 +0000
MIME-Version: 1.0
Content-Type: text/plain
Date: Thu, 14 Mar 2024 01:47:11 +0000
Message-ID:
<******@TYCP286MB0718.JPNP286.PROD.OUTLOOK.COM>

And for the love of god please update your error messages. "Please try again later" would never have helped me if the issue was due to things breaking because of some ridiculously large email chain.