Attachments upload

I think I might have seen ref to this issue on here somewhere in the past but I can’t find it, so apols for doubling up.

I’ve noticed this issue over a long time now so I thought it was about time to try to find out what’s going on.

I have a specific example - an email just sent.

It had two jpg’s attached, one 4.6MB in size and the other 5.1MB. Total upload should have been say 10MB, let’s say 15MB being generous.

I have a net meter app on my computer. I watched it, the Upload tab, as the email was leaving my computer.

It went through 10MB, 50MB, after about ten minutes it was at 100MB.

It finally made it into my Sent items folder after 152 MB.

I’d BCC’d myself and it came back in to my Inbox almost immediately, all 10MB of it. (that was the email size in my Inbox).

How did eM Client find another 140MB to send?


I suspect its to do with the way emails are packed / encoded and sent with the attachments.

See this thread post below.

attachment - eM Client


Apr '20

Attachments in email are encoded in MIME (base 64), and it increases the size 30-40 pct. You may try to ZIP the attachment, but it depends on what filetype you are attaching, if it can be compressed.

Also check that you are using a recent version of eM Client as there has been alot of fixes / updates.

Note:- If you do update to a later version, backup first via “Menu / Backup”.

Thanks CZ & Steven,

Steven - as absurd as it sounds, the figures are accurate. The net meter is accurate, nothing else was running on the computer at the time. It just went on and on and … until it finally made it into Sent. Yes agree, I too don’t normally send large attachments (although at 4.6MB plus 5.1MB I don’t think that’s large) … these were just two photos to my partner - she’s currently stuck in another country due to the global cold. The reason I used email as opposed to WhatsApp which I’d normally use is that I wanted to make it easier for her to see them on a big screen. As you say, for large stuff, say 25MB+, I’ll always avoid email and use DropBox or tresorit (yep, used it a lot) or more likely etc.

CZ - 8.2.1473 and not that it will make a difference, but 21H1 (19043.1237). The thing is, this isn’t a one-off. I’ve noticed it with eM C since I started using it … never seen it with any other email client. Most have an overhead but nothing like this. Over the past few days I’ve done a couple of tests. I have a simple 25MB file. I’ve sent it both bare and 7-Zip’d. Interestingly there is no difference between bare or zipped. There is a 100% overhead. What I mean is that whether I send the single file bare or zipped, almost exactly 50MB leave my computer before the email moves from Outbox to Sent items. That’s a huge overhead, but nothing like the crazy numbers I got when I sent the 10MB jpg’s with 1,000’s % overhead.

This is obviously not a huge deal … and a classic FWP … but it’s got me intrigued as to how eM C manages to find well over an extra 100MB to send when sending a 10MB email.

Many thanks again. Sorry this was long.

You do know that eM Client supports cloud attachments, right?

With this method, the attachments are automatically uploaded to your cloud service, and a link is inserted in the message instead.

To see more about this, check out out blog

Were there any upload errors? If so, it may be that the process was repeated before the server gave a confirmation that the message was uploaded.

Are you sure that when you clicked Send, 100MB was uploaded to the SMTP server from eM Client? Is your application giving bandwidth per application and differentiating between up and down?

Thanks Gary,

Were there any upload errors? No.

If so, it may be that the process was repeated before the server gave a confirmation that the message was uploaded. It was a steady send. It’s just that it never seemed to end. Until it finally did. Not the first time it’s happened (which is why I’ve finally posted on here) but certainly the biggest discrepency between actual email size and bytes sent. Biggest by far. I’ve had examples, say around a 10MB email, use 40+MB to get away from the computer quite a few times.

Are you sure that when you clicked Send, 100MB was uploaded to the SMTP server from eM Client? Yep. Definitely.

Is your application giving bandwidth per application and differentiating between up and down? Yes, all clean and clear. eM C was the only thing running on the computer at the time - no browsers etc. And yes, it tracks Up, Down and Total. As you’d expect, the Down was just ticking in periodic hundreds of bytes but it was the Up that was going for it. I just sat looking at it wondering what it could possibly be uploading. As I’ve done in the past.

Thank you.

Which seems like there was repeated attempts to upload the file. Could have been a temporary connection issue, or something on the server. You can look in Menu > Operations and see if there are any errors in the Log tab.

If it happens regularly with this provider, then you might want to contact them.

domingo 19 septiembre 2021 :: 1140hrs (UTC +01:00)

Hi @FlyHigh & @Gary

"This is obviously not a huge deal … and a classic FWP … but it’s got me intrigued…"

Me too! I’m at the airport in Sevilla with my wife so perhaps I am missing something because if I had an FWP/ACD (Amigos con derechos) I would keep quiet about it as my wife would definitely be ¡enfadado!

If you don’t understand Google: ¿Qué son los amigos con derechos?

¡Saludos desde la soleada Valencia en España!
¡Mis mejores deseos y mantente a salvo!


Hablo primero español, portugués e inglés, con conocimiento de varios otros idiomas.


After doing my own tests using Net Meter & eM Client V8.2.1509 for Windows with multiple attachments taking into account packing up the email before sending, I haven’t found any issue at all. I suspect as @steveshank says Net Meter on your computer is not calculating correctly on your computer for some reason and something else is causing the extra upload data in Net Meter.

eg: Using a stock Windows 10 V 21H1 with an 18mbps U/L NBN Speed connection, i created an email with 2 file attachments (1 x 5.4mb) and then other (8.1mb) (attached from my local drive) and when these sent the data all up was just on 20MB total (via Net Meter). Tested that multiple times and same result. Also both times i tested sending emails the email time to send all up with those 2 x attachments was only aprox 2mins.

So I would be looking at (what else is running in the background) on your computer as sounds like to me some unknown process is creating the extra data when you are sending email and causing Net Meter to show more upload data than normal. Nothing wrong with eM Client.

Cheers CZ & Gary

Done a video but I’m zonked … approaching midnight here … so will put it up on YT tomorrow.

To our Spanish friend Mr Skybat who popped up from the airport … I had no idea what you said but whatever it was gave me a laugh so I’m glad you chimed in.

And for the benefit of the others, I’ve just run it through the translator.

“Friends with benefits
pissed off!
What are friends with rights?
Greetings from sunny Valencia in Spain!
Best wishes and stay safe!
I speak Spanish, Portuguese and English first, with knowledge of several other languages.”

So now we all know!

Good-night (or -morning, -afternoon, -evening, -day … pick the one that works for you) all.

domingo 19 septiembre 2021 :: 1910hrs (UTC +01:00)

Hi @FlyHigh

I’m back home now and it’s 24°C & sunny, don’t know where you, however, have a good one tomorrow.

The reason you get “Friends with rights” is because the translator does not understand,
Spanish (in English idiomatic expressions) you got it right first time with “Friends with benefits”

In Spanish the literal translation of ‘derechos’ is rights.

¡Saludos desde la soleada Valencia en España!
¡Mis mejores deseos y mantente a salvo!


Hablo primero español, portugués e inglés, con conocimiento de varios otros idiomas.

Have you tried turning off you antivirus, or firewall? Perhaps it is fighting with EMClient on the send. Clearly there is something strange going on with your system which is different from most other systems.

thanks. Interesting and I wasn’t aware. But will probably continue to use tresorit or my Spideroak backup. E2E encryption. I want to present the safest examples to my clients. I tried it with Dropbox and it works just fine.

Guys, OK, another day. Just a couple of quick comments to get us all on the same page. When I say “quick”, I’m afraid this may actually become a TLDR thing; my apologies.

  • thanks so much for all your input, thoughts and assistance generally. Outstanding support on this forum as always.

  • this isn’t a rookie/amateur mistake. What I mean is I really don’t think that it is. I know it’s tempting to go to the easy/obvious stuff - that’s what I would do if I were you - but we’re way beyond that. If the issue was at that level I’d have fixed it easily and I wouldn’t be on here. I’m sorry that sounds big-headed/arrogant, but I’ve been wrestling with how to express it and I can’t think of a better way. (And I know that by saying that, I’ve set myself up totally such that if and when the reason is found, it will turn out to be something stupid on my part!)

  • so that means things like: 1. there’s nothing else running that could be contributing to the phantom upload count. 2. NetMeter isn’t playing up and showing erroneous data. 3. It’s not, for example, an AV thing. I won’t explain why, but believe me, it’s not. I do of course have a fully active firewall, but that’s not the issue either … eM C is fully allowed through.

  • to CZ’s last post. I think you’re right, it’s not eM C per se, but having been observing and trying to understand this and resolve it for so long, I feel that it is in some way eM C’s implementation on my system, both local (my computer) and remote (my email provider). I think that perhaps it’s the way eM C plays, and what I mean by that is maybe doesn’t play well, with GoDaddy’s whole MS 365 Exchange set-up. If that’s the case, it wouldn’t be affecting only me - it would be the same for everyone using eM C with GoDaddy’s recent forced move to 365 (having dropped its WorkSpace which went back to the last millennium, 1998 or so). But 99.5% of people would simply never notice. They’d send an email with a 15MB attachment and off it goes, not knowing or caring that in fact 30MB or 70MB or 110MB of data actually left their computer.

  • I’ve observed this over many months and these are the things I know. As with most people, the vast majority of my emails are small … a few KB’s … text only or maybe a PDF or whatever taking them to perhaps a couple of hundred KB’s. At sizes this small, you’d never notice an overhead on sending.

  • It’s when I send an email with say 15MB’s worth of jpg’s or MP3’s etc that things start to get interesting. The minimum overhead I ever get is very close to 100%. In the video I’ve put up on YT, a 25MB zipped file uses 49MB SMTP to get completely off my computer. So, basically a 100% overhead there.

  • I did that YT video last night. This morning I did another test - I sent myself an email with 4 x MP3’s, totalling 19.8MB in size. Exactly 49.8MB left my computer before the email made it into Sent. That’s again a 100% overhead. Then I deleted it from Sent and my Inbox because of course it had come in. I cleaned everything up. And I tried it again.

  • This time, 192MB left my computer before the email made it into my Sent folder. I know that’s hard to believe, but trust me if you will - 192MB to get a 19MB file away. I just sat here watching it and waiting for the Upload number on Net Meter to stop rising. It stopped on 192MB and at exactly the same time, the email appeared in my Sent folder.

  • re last night’s video I’ve put up on YT. I’m probably the last one to be paranoid about my email address being publicly visible, but it does concern me a bit. In the test, I did what I could to hide my email address but there’s simply no way around it. My address is visible in the video. I’ve set the video up as ‘Unlisted’, not ‘Public’ or ‘Private’. With Unlisted, anyone can see it if they have the link. I could put the link on here and you guys could see it but of course the rest of the world could also see it. But since the rest of the world doesn’t spend its day trawling through eM C’s forum looking for accidentally published email addresses, there’s really no problem. With that said however, I’d feel better if I could get the link through to just you four. Is this possible?

Thanks again and as always.

lunes 20 septiembre 2021 :: 1334hrs (UTC +01:00)

Hi @FlyHigh

I have become intrigued by your continuing phantom mb’s.
I too have run a number of tests as described by @cyberzork and confirm his findings, the only difference between his and my tests was the size of the files used (sligtly larger) & U/L speed where mine is 110Mbps. The sending time was virtually instantaneous. Same version of eMC with Win 10 Pro Workstation x64 21H1 on a very high spec Lenovo laptop, but that shouldn’t have any effect. I carried out the tests on a direct connection and via VPN with and without anti-virus enabled, also to IMAP & POP accounts, with and without encryption. All results more or less in the same ballpark.

Personally I wouldn’t bother to try to find out what is happening, but then your need is your affair.

¡Buena suerte!

¡Saludos desde la soleada Valencia en España!
¡Mis mejores deseos y mantente a salvo!


Hablo español, luego portugués e inglés, con conocimiento de varios otros idiomas.

1 Like

Yes, I have to agree with the others; I was not able to reproduce this.

So it appears that as you said it was taking so long to send, that the message was repeatedly uploaded to the server, until the server agreed it had received it.

1 Like

Thank you everyone.

Given that none of you have ever experienced this, nor can you replicate or see any evidence of it on your systems, your efforts, suggestions and general stick-with-it-ness go above and beyond the call I feel. CZ & Skybat - your attempts to replicate it are much appreciated.

I know what will happen - I’ll solve this mystery but it will be accidental and random! I’ll wake up in the middle of the night with an “Ah ha!” moment, or I’ll see reference to it somewhere obscure, perhaps someone else experiencing a related issue, long after I’ve given up looking for the solution.

At this stage, I’m still thinking it’s perhaps happening as a result of the combination of eM C, GoDaddy and MS 365 Exchange. Ah, a thought … do either of you CZ or Skybat happen to be using that same combination? I’m guessing not. If so, there goes that theory!

BTW if any of you still want to see the video which runs for just 1:58, let me know. It shows clearly the 100% overhead on a 25MB compressed file. I haven’t made a video showing the test where it uploaded 192MB to get a 19MB email into my Sent folder. That’s a 1000% overhead!

As always, you have my sincere gratitude gentlemen.

martes 21 septiembre 2021 :: 1222hrs (UTC +01:00)

Hi @FlyHigh

I am still intrigued by the whole situation, have just read through all the posts and have a few questions/comments (some tongue in cheek). I took early retirement a few years ago from the computer support company I founded in 1993 and still own, so have all the time in the world except when there is a distant problem and nobody wants to travel so they call me; today we have thunder & lightening, I can’t go out on my JetSki so perhaps I can do something useful. My son and a team of colleagues now run the company I stay away as much as possible - they refer to me as maldita pesadilla! (won’t translate here’s a clue 'king nightmare)

The company do not use GoDaddy or MS 365, they do use exchange. I have no idea if any of the clients have the combination though I do know none use eMC.
However, that’s another story as they were about to start a 30 seat eMC feasibility study which if OK would mean a move to 250+ seats within the company then Covid struck, now they have decided to wait until v9 of eMC is released.

Nowhere have you mentioned your internet connection speed; what is it?
@Gary has suggested that repeated upload attempts to the server (you stated that it takes a long time) might cause a ‘totting up’ of mb’s.
You said that you are using Win 10 21H1, what about the computer itself? Grabbing at straws now.

You say that you tried an email with a 25mb file, that’s larger than the norm, did you have an upgrade with GoDaddy to do this? Also I am sure you are aware that attachments increase in size by up to 50% because of encoding, for instance a 10mb file could grow to 14mb. (just a thought keeping this in mind, if your system is making repeated attempts to send as @Gary queried, could this be an explanation for the mb growth?)

In your post you quote a @cyberzork post. "I think you’re right, it’s not eM C per se"
‘Per Se’ is a well known cafe/restaurant in Oviedo, Asturias, the birth place of Fernando Alonso, there are also museums that are well worth visiting, a great place. The region is known for over 50 cheeses with a visit to the Cheese Caves being worthwhile.
My favorite ‘Per Se’ is in New York a 3star Michelin restaurant that is a must! It overlooks Central Park at the Columbus Circle.
Travelogue over.

Enough rambling on, plus the weather has cleared so I’m off to JetSki.

¡Saludos desde la soleada Valencia en España!
¡Mis mejores deseos y mantente a salvo!


Hablo español, luego portugués e inglés, con conocimiento de varios otros idiomas.

Thanks Skybat for your latest.

Going through the points in sequence -

  • I have various line speeds I use depending on where I am and what I’m doing at the time, varying from about 40Mbps (down) to about 220Mbps. So that’s about 5MB/s to 27MB/s down. They’re async but as you’d know, async doesn’t mean what it did back in the early days of ADSL2+. These are wireless and sometimes up can be faster than down. All depends. When I made the YT video showing a 25MB file using 50MB of upload to send, a 100% overhead, I chose a slow line so you can see the bytes ticking over. That 50MB took about 50 seconds to upload.

  • but the issue isn’t caused by repeated upload attempts. I can’t prove that to you, but trust me if you can; it’s not.

  • re the computer, I’ll attach here a userbenchmark run and you can see the specs on there. I know everyone loves to hate userbenchmark because they supposedly hate AMD (which is patently not true) and for various other ‘we just love to hate userbenchmark’ reasons, but it’ll show you my computer details.

  • but line speed, computer, line errors etc I think are not factors. Again I can’t prove this but I think if I tested it on dial-up on a Windows XP machine I’d see the same strange behaviour as on a system with the fastest of everything.

  • re the file size, 25MB will get through both GoDaddy and 365. They start to get a bit tetchy around 30MB.

  • Per Se is a great name for a restaurant and I figure if I can get new tyres fitted (I run Michelin PS4) while eating the world’s most expensive meal, well, that might make me feel a bit better when it comes to bill-paying time.

Cheers Skybat,

Ah, I keep forgetting, no attachments on here. So here’s the PDF