Message with 11mb attachment gets stuck in Outbox and stops subsequent messages

Ver 8.0.3385.

I’m using eM Client with an Office365 email account. I have problems sending messages with attachments. In this case a 11mb file. I can use the web client and send this file, so there isn’t a problem with size limits on the account.

I watch the Operations window and it shows that it is sending. There is no error message. I look at the log and after approximately 2 minutes it shows the message being sent, I see "Exchange Web Services Uploading item(s) to folder ‘/Drafts’ "

The message is not in the local or online Drafts folder. It remains in the Outbox. Messages composed and sent after the problem message just end up queued in the Outbox and not processed until the problem message is deleted.

Please help, and I’d rather you don’t suggest I use wetransfer or other cloud service - an 11mb file is in no way a size that should need to use such a service.


As far as I know the size limit for Office365 is 25MB when using an email client, so 11MB should not be a problem.

The message may be stuck for some reason, so you may find an error in Menu > Operations, then in the Log tab.

If the message is stuck and causing a queue, delete it from the Local Folders Outbox. If Local Folders are not visible, you can enable them in Menu > Settings > General.

jueves 22 octubre 2020 :: 2053hrs (UTC +01:00)

Hi @Moyners

The default Office 365 maximum message size for messages is 25MB. However, you can change the maximum message size for an individual mailbox with the Office 365 Admin Center.

I had a similar issue a while back and discovered that, and I don’t know how, the default message size had mysteriously changed down to 2.5MB.
I found the following and was able to reset the message size (you will be able to see what the limit is set to on your system); you can go up to 150MB though bear in mind that if you send a very large message the transmission time will be connection speed dependant and might also cause problems for the recipient.

This link gives video instructions

¡Saludos desde la soleada España!


Thanks for your replies - as I said in my message, I was able to send the 11mb file when using the office365 web client, so I don’t have attachment size issues with office365.

Any more thoughts as to why eMclient might be behaving like this?

There will be an error in Menu > Operations > Log tab. Look for SMTP errors, but it is unlikely anyone here will be able to decipher them, except to confirm that there is a problem with the communication between eM Client and your server.

One thing you can try is to completely disable your anti-virus application and any VPN or proxy you are using, and see if you can sent the attachments from eM Client.

Thanks, Gary, there is no error shown. I will, though, try with the AV disabled and report back.

I’ve just now tried with AVG and Malwarebytes turned off. Same behaviour - no errors, just shows it moves message to Drafts.