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Reasonable Size Limit for MX

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mail at oliwel

Sep 8, 2009, 4:57 AM

Post #1 of 8 (2315 views)
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Reasonable Size Limit for MX

Hi All,

todaay, a customer started to argue with me, that a 20MB Size Limit is
much to small for his needs and "everybody" else has much huger limits.

I got 20 MB teached by a friend as a golden rule of thumb, however this
is some years ago and some quickly testet systems show a range from 5 to
even 100 MB as response on the "EHLO" command.

So easy question, is there any suggestion, rule, common sense about the
max email size setting or is this perfectly my thing. Would I encounter
any problems raising this to 50M or even more?

TIA

Oliver

--
Protect your environment - close windows and adopt a penguin!
PGP-Key: 3B2C 8095 A7DF 8BB5 2CFF 8168 CAB7 B0DD 3985 1721

qmail-08 at jeremykister

Sep 8, 2009, 6:01 AM

Post #2 of 8 (2190 views)
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Re: Reasonable Size Limit for MX [In reply to]

On 9/8/2009 7:57 AM, Oliver Welter wrote:
> So easy question, is there any suggestion, rule, common sense about the
> max email size setting or is this perfectly my thing. Would I encounter
> any problems raising this to 50M or even more?

10MB is the hard cap for many thousands of domains I help run.

there are many other mechanisms for file transfer for folks who don't know
how to ftp -- like yousendit.com

--

Jeremy Kister
http://jeremy.kister.net./

johnl at iecc

Sep 8, 2009, 6:20 AM

Post #3 of 8 (2192 views)
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Re: Reasonable Size Limit for MX [In reply to]

In article <4AA646B4.7040700 [at] oliwel> you write:
>Hi All,
>
>todaay, a customer started to argue with me, that a 20MB Size Limit is
>much to small for his needs and "everybody" else has much huger limits.

Uh huh. gmail limits mail to 20MB, yahoo and hotmail to 10MB

Like people said, there's other ways to move giant files around.

R's,
John

kyle-qmail at memoryhole

Sep 8, 2009, 9:06 AM

Post #4 of 8 (2188 views)
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Re: Reasonable Size Limit for MX [In reply to]

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Hash: SHA256

On Tuesday, September 8 at 01:57 PM, quoth Oliver Welter:
> todaay, a customer started to argue with me, that a 20MB Size Limit
> is much to small for his needs and "everybody" else has much huger
> limits.

I suppose it's worth pointing out that sending files via email is
horribly inefficient. In order to encode a file so it can be attached
to an email, it must be transformed into ascii characters (usually
with base64 encoding), which essentially adds 37% to the size. A 20MB
file becomes 27.4MB (or so). A 100MB file becomes 137MB. That's one
reason attaching large files to emails isn't a good idea.

Another reason is because of spam scanning. For example, lots of
people use SpamAssassin, which has problems scanning large messages.
By problems, I mean it can bring your server to its knees, use up
almost all available memory and CPU cycles. It's not pretty. It's so
bad, that by default, the spamc/spamd setup simply refuses to scan
messages any larger than 500k. I haven't looked into it in depth, but
I imagine other deep analysis programs have size limits as well.

Now, you may say "sure, but what spammer would send such large
messages?" That's what I said until I started getting waves of spam
messages that were over ten megabytes each. The thing to remember is
that spammers don't have to pay for bandwidth; they don't actually
care how big messages are, and large images are a convenient way to
skate past many anti-spam tools.

> I got 20 MB teached by a friend as a golden rule of thumb, however
> this is some years ago and some quickly testet systems show a range
> from 5 to even 100 MB as response on the "EHLO" command.

Fundamentally, email hasn't really changed at all in the last twenty
years. It's gotten more widespread and more spam-infested, but the
basic realities haven't changed. Your friend's advice is as good now
as it was then.

~Kyle
- --
Those who agree with us may not be right, but we admire their
astuteness.
-- Cullen Hightower
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kyle-qmail at memoryhole

Sep 8, 2009, 9:09 AM

Post #5 of 8 (2184 views)
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Re: Reasonable Size Limit for MX [In reply to]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

On Tuesday, September 8 at 01:20 PM, quoth John Levine:
> In article <4AA646B4.7040700 [at] oliwel> you write:
>> Hi All,
>>
>> todaay, a customer started to argue with me, that a 20MB Size Limit is
>> much to small for his needs and "everybody" else has much huger limits.
>
> Uh huh. gmail limits mail to 20MB, yahoo and hotmail to 10MB
>
> Like people said, there's other ways to move giant files around.

Something that occurred to me as a way to look at this: who is this
customer intending to SEND messages to? It's essentially impossible to
send a 30MB file to a gmail account; it'll just sit on your server
being rejected until the queue lifetime expires. There's not much
advantage to accepting really large messages into your own queue
(generally) since often times, they can't actually be delivered.

~Kyle
- --
A fanatic is one who can't change his mind and won't change the
subject.
-- Winston Churchill, July 5, 1954
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lists-qmail at maexotic

Sep 8, 2009, 9:56 AM

Post #6 of 8 (2189 views)
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Re: Reasonable Size Limit for MX [In reply to]

On Tue, Sep 08, 2009 at 01:57:40PM +0200, Oliver Welter wrote:
> todaay, a customer started to argue with me, that a 20MB Size Limit is
> much to small for his needs and "everybody" else has much huger limits.

I remember a customer who had unlimited size limits.
He changed his mind, when a PR agency produced a 200 MB ZIP file of
images, PDFs and office documents and sent it to the contact person at
that company ... and via Cc: also to about 10 other people in that
company they had the email addresses of.
The hard disk of their internal mailserver and their boss weren't too
amused about that and limits were put in place.

I guess "resonable" would be the result of a function taking number of
users, size of hard disk and network bandwidth in account.
Oh and the same limits should be set for both directions (incoming
and outgoing).

\Maex

bh at izb

Sep 8, 2009, 3:06 PM

Post #7 of 8 (2203 views)
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Re: Reasonable Size Limit for MX [In reply to]

Oliver Welter <mail [at] oliwel> writes:

> Hi All,
>
> todaay, a customer started to argue with me, that a 20MB Size Limit is
> much to small for his needs and "everybody" else has much huger limits.
>
> I got 20 MB teached by a friend as a golden rule of thumb, however this
> is some years ago and some quickly testet systems show a range from 5 to
> even 100 MB as response on the "EHLO" command.
>
> So easy question, is there any suggestion, rule, common sense about the
> max email size setting or is this perfectly my thing. Would I encounter
> any problems raising this to 50M or even more?

Daum, one of email service company in Korea, do not use SMTP for huge
file size. Daum only provides file download link (HTTP) to customers
with limiting time (about 7 days). That's engough to customer.

Sincerely,

--
"But his ultimate aim is to enter that society with a certain power since
society doesn't really protect its members who do not have their own
individual power."
-- Michael Corleone, "Chapter 25", page 363

mducharme at cybergeneration

Sep 9, 2009, 8:42 AM

Post #8 of 8 (2161 views)
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RE: Reasonable Size Limit for MX [In reply to]

> -----Message d'origine-----
> De�: Oliver Welter [mailto:mail [at] oliwel]
> Envoy�: 8 septembre 2009 07:58
> ��: qmail mailing list
> Objet�: Reasonable Size Limit for MX
>
> Hi All,
>

Hi Oliver

> todaay, a customer started to argue with me, that a 20MB Size Limit is
> much to small for his needs and "everybody" else has much huger limits.

We have a 20 MB limit, and yes we have some customers say it is too low.

Everybody else have their own limits which is NOT necessarily bigger.

>
> I got 20 MB teached by a friend as a golden rule of thumb, however this
> is some years ago and some quickly testet systems show a range from 5 to
> even 100 MB as response on the "EHLO" command.
>
> So easy question, is there any suggestion, rule, common sense about the
> max email size setting or is this perfectly my thing. Would I encounter
> any problems raising this to 50M or even more?
>

For those who complain I simply suggest HTTP upload services like
http://www.sendspace.com/

They offer a 300 megs limit, you need to upload to HTTP server and it will
send an email with a link.

HTH

Maxime Ducharme

> TIA
>
> Oliver
>
> --
> Protect your environment - close windows and adopt a penguin!
> PGP-Key: 3B2C 8095 A7DF 8BB5 2CFF 8168 CAB7 B0DD 3985 1721

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