New user's registration have been closed due to high spamming and low trafic on this forum. Please contact forum admins directly if you need an account. Thanks !

Message size limit

Got problems with your B2 or B3? Share and get helped!
cgl72
Posts: 13
Joined: 25 Oct 2008, 10:17

Message size limit

Post by cgl72 »

I have used the admin interface to set up bubba to fetch mail from my professional email as a backup. You never know what can happen to a job these days, one cannot be too prudent...

But bubba has been responding the following message to the initiator of any large message. It is obviously confusing for my business contacts, who think the message has not been delivered to the primary address, when in fact this error is generated by my Bubba2:
-------- Original Message --------
Subject: Mail delivery failed: returning message to sender
Date: Fri, 19 Mar 2010 12:38:29 +0100 (CET)
From: Mail Delivery System <MAILER-DAEMON@bubba.localdomain>
To: xyz

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

bb@localhost
SMTP error: 552 5.3.4 Message size exceeds fixed limit

Reporting-MTA: dns; bubba.localdomain

Final-Recipient: rfc822; bb@localhost
Last-Attempt-Date: Fri, 19 Mar 2010 12:38:29 +0100 (CET)
Action: failed
Status: 5.3.4
Diagnostic-Code: 552 5.3.4 Message size exceeds fixed limit
How can I change this to either remove the limit or bring it up to the same limit as my current email provider?
Thx for your help
Christian
redw0001
Posts: 96
Joined: 07 Sep 2009, 14:03

Re: Message size limit

Post by redw0001 »

I wish to update the default 10MB maximum email size, I think the answer to this lies in the link in the response to the original poster, however the viewtopic does not work, just gets me some error. Can anyone point me in the right direction please.

A friend sent me an email with 27MB of attachments and my bubba sent him a 552 error message once every five minutes for a day and a half when I saw his email saying I had a problem and I purged the email on my ISP.

A better idea would be to send one email and trash the offending incoming. Cant find anything on this.

I tried to research this outside the bubba environment and came up with adding this to /etc/postfix/main.cf:

mailbox_size_limit = 0 <already exists>
message_size_limit = 52428800

Advice would be gratefully received.
Henri
Posts: 62
Joined: 14 Jul 2009, 07:56

Re: Message size limit

Post by Henri »

Hi

asparak's link points to an old forum address excito...
Here is the current location of that link (forum.mybubba.org).

http://forum.mybubba.org/viewtopic.php?f=8&t=2179
Gordon
Posts: 1461
Joined: 10 Aug 2011, 03:18

Re: Message size limit

Post by Gordon »

The 4MB size limit is historically set and still applies to many of the large MTA's on the net. Even the 8 to 7 bit UUencoding is because of this old infrastructure. That you can send bigger emails having your own MTA that does not impose this limit, and that a receiver that also has its own MTA also removed the limit, does not mean that you should actually start sending emails that size. ANY additional hop that you may require to get from your MTA to the other may impose this limit. An intermediate sending MTA may also not respond very well to the 552 SMTP message and go into a deadlock phase trying to deliver the oversized message to either the original recipient or return to sender.

The email protocol is about 50 years old and it is simply not designed to handle messages that big. Do be considerate and use the net wisely, so that anyone can enjoy it and not experience seizing of services that we've all grown to take for granted. And yes I'm talking personal experience here, having had all business emails suspended because someone was trying to get a 4MB attachment over a line that would not do more than 9.600 bit/s and failed numerous times during transfer.

If you do need to send bigger attachments, break it up in sections like they do in usenet (which is essentially the same protocol) or send a hyperlink from where the receiver can fetch the file using a more suitable protocol. Think FTP, or Rsync.
redw0001
Posts: 96
Joined: 07 Sep 2009, 14:03

Re: Message size limit

Post by redw0001 »

Gordon, Broadly I agree with your sentiments. I dislike intensely getting emails greater than a few MB.

However, I cannot stop people sending bigger emails. What I'm trying to achieve is to stop me flooding them with smtp error 552 emails (too large). My B3 checks my ISP for mail once every five minutes, attempts to download any emails, trys to get the big one (27MB), fails after 10MB and sends the guy an error message. It then goes to sleep for five minutes and repeats the exercise .... ad infinitum.

He contacted me after a day and a half away saying he had hundreds of emails from me.

In addition to disliking large emails (wetransfer or dropbox are far more sociable) I dont like to think my system is sending all these messages. Oh and each time the 10MB transferred the others in my house got very poor performance (no real surprise as best can do here is 5.1Mb/241Kb. (B and b used correctly).

I dont use Horde, I use roundcube, however, I think it is SMTP or Dovecot that needs something doing to it. I'd be happy to leave the limit as is if only I could stop the multiple messages going to anyone who sends me (to big) emails.

Personally, largest email I send is 5MB (one photo) then I resort to wetransfer, but not everyone does that.
Gordon
Posts: 1461
Joined: 10 Aug 2011, 03:18

Re: Message size limit

Post by Gordon »

That kind of changes things, as it appears that your ISP is at fault here accepting oversized messages that won't transfer throughout the whole of the internet. Ten to one they're using Microsoft servers for their infrastructure. Really bad behaving servers because Microsoft's vision has always been that if you have trouble connecting you should buy new hardware and preferably start using Windows yourself.

I didn't consider fetchmail because you mentioned a postfix error, but in this case I think your best option is to set the postfix limit to something ridiculously high. You may also ask your ISP what non standard message size limit they have set and use that number. Be aware though that being able to send oversized messages does in no way guarantee that others can receive those messages. In fact you may get very random behaviour depending on the path that your email takes to reach its destination.
Gordon
Posts: 1461
Joined: 10 Aug 2011, 03:18

Re: Message size limit

Post by Gordon »

Ubi wrote:He's not sending. He's just using fetchmail on his B3 to create a backup copy.
So although I understand your sentiment on oversized mails, this is not the place to rant about them. The problem is because his ISP is too lax for your standatrds,but this is not someting the OP can act upon.

In fact, for my own users I also set a rather high (25MB) mail size limit because it saves me a lot of helpdesk tickets from normal people who do not understand email, do not read error messages and do not care that the protocol was not designed for transfer of large files.
In a sense he is. Because fetchmail drops it on postfix for local delivery. And obviously I don't know which MTA he uses for sending, but whether that is his own B3 or his ISP doesn't really change the essence. Sending emails larger than 4Mb are not guaranteed to reach their destination. Ever. And while you may regard this as being a rant, this is about offering clarity to users and not have them ask why they can't send Mike the same email as they did Pete. You're better of with users understanding that there is a limit and work around this, than randomly having these limits imposed on them. e.g. people know they can't use more than 160 characters in an SMS and they don't make an issue out of it. They would though if some of them could send 300 characters instead.

And that's the whole point. Now you've got this guy that sent an email with a 27Mb attachment complaining that redw0001 is spamming him with 552 error messages and he doesn't even realize that he caused this himself and that his ISP should have stopped him in the first place. This is not an error, this is about misbehaving/incorrectly configured MTA's allowing this to look like an error. Which apparently includes your servers. Sorry.
Gordon
Posts: 1461
Joined: 10 Aug 2011, 03:18

Re: Message size limit

Post by Gordon »

I don't think you'd want to walk it, but relatively close it is.
redw0001
Posts: 96
Joined: 07 Sep 2009, 14:03

Re: Message size limit

Post by redw0001 »

"And that's the whole point. Now you've got this guy that sent an email with a 27Mb attachment complaining that redw0001 is spamming him with 552 error messages and he doesn't even realize that he caused this himself and that his ISP should have stopped him in the first place."

That bit sort of got the point spot on. Some investigation on my ISPs fora (forums?) revealed a limit of 100MB I believe. I put money on this being increased due to user demand and increasing performance in technology that results in limits being lifted without the thought process that is really necessary... (we now have 20Mb fibre so lets up the transfer limits, we now have 50Mb fibre so lets up the limits.... etc etc.) However, the poor soul out in the country where the fibre investment hasn't been made is still on 5Mb or less. SPLAT.

Please don't argue over my situation, I don't really interpret any of the discussion as a rant. The only thing I was pooped about was getting a complaint effectively of spamming, (my friend didnt actually say that but he was clearly a bit narked).

Now, my server (my B3) which collects all my emails is my responsibility and I feel I need to stop it sending out 'spam' even if it is caused by someone elses incomplete thinking (user, ISP or whoever).

Anyway, I'll have a fiddle with the limits to see if I can fix it and suffer my line being hogged by the inconsiderate :-)

Guys, thanks for the help.
redw0001
Posts: 96
Joined: 07 Sep 2009, 14:03

Re: Message size limit

Post by redw0001 »

So, I would not call downloading emails onto my B3 from an ISP mirroring. My understanding was I was downloading them. Mirroring is something completely different.

Apparently I am guilty. Guilty of not knowing there was a limit in the way the software was set in my B3.

subject closed. bye
Gordon
Posts: 1461
Joined: 10 Aug 2011, 03:18

Re: Message size limit

Post by Gordon »

AFAIK the current 'safe' limit is 10MB and this is the limit that postfix on the B3 is set to. Obviously this is 10MB in 7-bit encoding, which I suppose Ubi would get rid of as well if he could invent email today, and added redundancy, making the practical attachment size limit some 7.5MB.

In terms of guilt, I totally disagree. The ISP is the one to blame because they are the ones fully aware of stretching boundaries. In fact, according to Wikipedia, when Google extended their email size limit to 25MB they warned their users that people using other email services might not be able to receive those larger sized emails. Essentially: expect to get a 552 error in return if you cross the 'old' limit.

The cases presented here are only special in the sense that part of the email route is using a different protocol than SMTP. If using that other protocol is enforced by the ISP, then they are double to blame for not monitoring the responses from the next hop the email travels and simply assume that it is a desktop email application that will accept everything that doesn't cause it to crash.
Gordon
Posts: 1461
Joined: 10 Aug 2011, 03:18

Re: Message size limit

Post by Gordon »

RFC does not specify a limit. However, as email is a store and forward protocol, there is and always has been a practical limit. These limits are well known, or at least should be considered well known among the technical incrowd. If you set a higher limit then you are deliberately taking a chance that some other MTA along the path will bounce a message that you should have stopped being the point of entry.

So what do we have here? There is at least one ISP accepting oversized emails and there's a customer using fetchmail to send the email on to another MTA that is not altered similarly. Now your point of view is that this customer is supposed to use the same advanced settings that you set, while at the same time you made those advanced settings because customers don't understand that there are limits. Translation: first you consider your customers to be idiots, annoying complaining idiots, and then you call them idiots for not doing the same thing you did.

Being a Bubba user you should know better. You know damn well that many users never go to console and fully rely on the web interface - which does not offer the option to extend the message size limit of postfix. There are lots of other NAS and SBS-like solutions, such as ClearOS, that are built similarly and will cause the same issues if you as an ISP break the SMTP path to the customer's premises and they need to use pop or imap protocols to load the messages onto their local MTA. Again, the cause of the issue is not the customer not following the ISP's standards, but the ISP deliberately taking the chance of the mail bouncing because of its size somewhere along the path.

PS Who said redw0001 didn't set his ISP's SMTP server as outgoing email server (smarthost)?
Ubi
Posts: 1549
Joined: 17 Jul 2007, 09:01

Re: Message size limit

Post by Ubi »

I'm not getting pulled into one of these stupid flame wars again. I removed my posts from this thread.
redw0001
Posts: 96
Joined: 07 Sep 2009, 14:03

Re: Message size limit

Post by redw0001 »

Gordon,
Thanks for your help and patience, I'd not planned to add more however, just in case others do see this here is my current position. Yes, I do use their smtp server, it is coded into my B3 via the admin GUI.

I have changed th maximum as I stated earlier and logging on with Telnet to port 25 I see it changed dynamically, I used EHLO to check. So now I have a 50MB limit, which I am not happy with but it will reduce the chance of this happening again. This is only set this big to allow incoming large emails. I do not send large emails out, maximum size of one photo (about 5 MB for me).

I originally set up this service on my B3 as I'm not keen on all my data being stored on other peoples servers, that includes my email correspondence. The User Manual seemed pretty clear and easy to follow and having been used to a lifetime of following IBM manuals I saw no warnings or guidance on SMTP configuration changes needed. I gues that was an assumption too far made by me.

A challenge I see now is what if my ISP makes other changes, they dont tell me but they could break something else.

What interests me is how do you stop the repeated attempts at downloading that I got into. I've been trawling the internet and drawn a blank so far. This must happen between ISP else there would be files blocked Nd reattempting all over the place and millions of 552s flying around. I must be missing something.
Post Reply