Unaccountably high e-mail usage

[#1]

I have noticed that my usage in recent months seems to have doubled, so I clicked on the breakdown to see if I could identify the problem. To my amazement, 60% of my usage is e-mail. This puzzles me because I'm not aware of sending a large volume of e-mail, perhaps one or two in plain text every day and I only receive about 1MB per day. I have filters set not to download messages which are obviously spam and they are just deleted from the server without being downloaded. Yet according to Plusnet's figures I am sending or receiving over 100MB of mail per day, 100 times my estimate of traffic.

My router is secured and there is no port forwarding for mail set up, and I haven't seen any unusual activity on the router lights, so I'm at a loss to understand where this traffic is coming from.

What could be causing this?

[#2]

Any chance you could be infected with malware that is using you as a mail source for spam?  Do you have up to date antivirus installed etc? It could be small bursts over 5 minutes to send a lot of mail so you not seen on your router any difference in the lights.

Other possibility is if something has been using the same port as mail (not quite sure what!) and being classed like that.

[#3]

How frequently are you checking for new mail in your mail client? Are you using IMAP or POP3?

There's a certain amount of data usage each time your mail client polls the mail server, even if there are no new emails.

[#4]

I'm using Linux, so it's not likely I have any malware installed, though, of course, not impossible. PN could check the logs to see what has been sent or received on my account. Obviously, spam would be a problem if it were happening.

I check for new mail every 10 minutes by POP, so 6 x say 18 hours would be 108 checks/day. I can't believe each check takes 1 MB of data when the content of messages and (mostly) headers downloaded is only about 500 KB for the whole day. That wouldn't be very efficient. Anyway, this usage hasn't changed in years.

I had hoped someone from PN would look into this, as I would like to know what's using all this bandwidth before it consumes my whole allowance.

[#5]

@kjpetrie - Out of curiosity I checked my usage on both of my DSL accounts when I saw this post earlier. But in my usage I have nothing for email, on both accounts and one account that had 43G of data usage (the other having just rolled over) not one single kilobyte was marked as email. I’m on Mac and I have 5 (IMAP) email accounts polled every 10 minutes!

It may be that as I use my own mail server it doesn’t get counted but all accounts use ports 993 / 465, so how this traffic is identified I can’t say.

[#6]

Please check your PlusNet Broadband Firewall is active, set to "low" at the very least.
You can find the settings in the Member's Centre, under Connection Settings.

[#7]

I have now established by monitoring network usage on my PC that Thunderbird downloads about 3 MB of data when checking e-mails - so I have found the culprit. Now I just have to understand why this is happening before it consumes all my bandwidth. I have temporarily dropped the frequency of checking to hourly. The mail stored on the server is only 319 KB, all read, so why would TB need to download 3 MB every time it checks?

What is it downloading?

Aha! I think I've found it! I had seven "identities" (e-mail addresses I can choose when sending. And TB has a separate listing of the POP server for each one. I deleted an identity and one of the server entries disappeared. So I reckon, although identities are about sending, not receiving, it's downloading all the messages on the server for every identity, despite the fact there is only one shared inbox for them all.  Moreover, it's not just downloading the headers, by the looks of things, but the whole message seven times, whether it needs it or not. Other TB users might want to check, especially if they have multiple identities. I need to check this further.

Could this explain why PN's mail service has suddenly run into capacity and bandwidth problems, I wonder?

[#8]

I reckon @bobpullen might be interested in your findings!

[#9]

Could you manage without using identities and instead use the Customise from address on drop down on the From box when composing a message?

Also you must be leaving the messages on the server for a long time. With POP3 you'd normally set it to delete after a few days which would reduce the amount of mail downloaded by each identity.

If you do want to leave all the mail on the server you'd be better off using IMAP - that would only pick up new messages.

[#10]

I'm still investigating this issue. I had TB set up to delete messages after 14 days, but found there are still messages on the server dating back to 2014! This impedes further investigation as any attempt to set up a new account or change to an IMAP account just results in an attempt to download 85,000 messages, all of which are already stored on my PC and backed up. I don't know why messages are not being deleted, or whether that is a TB problem or a PN one. That'll need more study too, but I can only do this overnight because of the huge bandwidth implications of processing so many messages.

I have tried to deleted all the old messages using webmail, but that doesn't work because there are too many and an attempt to delete them all causes an internal server error (either the process takes so long it times out or the task is too big for the available memory). I can delete one page at a time, but that's only 200 out of 85,000 and will clearly take too long.

I tried setting up a new TB account running overnight with filters set to delete all messages, but it crashed after a few hours complaining a message didn't exist and when I logged in with webmail they were all still there.

I have set up IMAP and will run TB again tonight to see whether it will download all the messages, and tomorrow night I'll try to tell it to delete all the old ones - if my PC doesn't run out of memory in the attempt!

[#11]

@kjpetrie

Try using the basic webmail (SquirrelMail) - I think it lets you set the number of messages per page much higher than 200.

[#12]

I've just tried what I suggested and it worked. I loaded up a Plusnet mailbox with 1500+ messages (copied in from other places) and was able to select and delete 1000 messages using Plusnet's Basic Webmail (https://webmail.plus.net/squirrelmail/src/login.php). In the Options, Display Preferences there's an option Number of Messages per Page and I was able to set that to 1000.

After you've deleted messages and refreshed the Trash folder there's a purge link appears to empty the deleted items from Trash.

[#13]

Thanks. My struggles at setting up IMAP are finally complete - I think. I didn't see your post until I'd finished, unfortunately,  but I did manage to get them all deleted in the end, though I did it mainly by leaving Thunderbird on overnight and letting it download and delete all the messages. Used 1GB of data overnight and then another 600MB today tidying up. Now to see how things go with IMAP. I've turned off periodic downloads and turned on the IDLE protocol instead, so I'll see what difference that makes. Periodic checking seemed to involve a 2 or 3 MB download before it started looking for new messages, and I'm still not clear what that was. It's still set to do a download on launch and then I rely on the server notifying it when a new message arrives. The proof will be in what happens to my bandwidth use now. I'll watch and report after a couple of days.

[#14]

Have you emptied the deleted (trash) folder?

[#15]

Yes. My impression is that I'm using a lot less bandwidth now, but I'll need to watch the stats for a couple of days to be sure. IMAP does seem less reliable than POP3, probably because more happens in real time so if the server doesn't respond in a timely fashion it's much more noticeable. Several times I've had the process hang when I've tried to read an unread message, had to close the message pane and try again in order to persuade it to download. Hope that's not going to be too annoying.