Can't Attach Large Files to Outgoing eM Client Emails

On my Win 10 computer, I have no problem using eM Client to send emails with a small attachment. For example, I successfully attached a Word file of size 13 KB and a jpg file of size 130 KB. But when I tried to attach a larger jpg photo file of 800 KB or a 7.8 MB avi video, the sending stops about half way thru and the email stays in my Outbox. On this computer I use Defender and Malwarebytes Premium, and the paid version of eM Client 7.2.34711.0.

Now, on my older Win 7 computer I have no problem sending any of the above-mentioned attachments. On this computer I use Microsoft Security Essentials, Windows Firewall, the free version of Malwarebytes, and the free version of eM Client 7.2.34711.0.

Does anyone have any idea why I can't attach larger files on my Win 10 computer but can on my Win 7 computer? If the larger outgoing emails are being blocked by one of my AV or security components, how do I stop this from happening? Thanks in Advance

I get a warning but, it still goes...

Edwin, I get that message on my Win 7 computer and, like you, the email w/attachment still goes out. But on my Win 10 computer, no message and the email is never sent....the progress bar just stops and hangs.

dalchina, I have requested Pro support before, and I am getting ready to do so now. They don't always understand my problem and it takes them a couple of days to respond. I was hoping to get a quicker response on this forum from someone using this email client. I really do miss Windows Live Mail.

dalchina, I don't know as I never used Thunderbird. After using Windows Live Mail for many years, I had accumulated many messages, contacts, and email accounts. eM Client made the importing of all this data very easy, whereas from what I read that was going to be a very laborious task using Thunderbird. That said, Thunderbird would probably have been my 2nd choice, as I really don't like Mail.

Yesterday I contacted the eM Client Pro Help Desk about my problem of not being able to send emails with large attachments. This morning I got a reply asking for a screen shot of any error message (there were none) and a copy of the Operations Log file.

So I thought I would try once again in order to send them a current Operations Log. But this time the send worked! Twice I successfully sent an email with a rather large video file attached. I had tried to send each of these before with no success.

But this time both were successfully sent in a very reasonable time frame (for my slow DSL). I don't know what happened to correct the situation, but I am now a happy camper.