Exchange Server 2010 unable to send email with attachment larger than 20 MB


My Exchange Server is somehow not allowing users to send out email greater than 20 MB to external email ?
Internally it works great with no issues.

I've also tried with 18 MB file to my free email account but it is rejected with the following error:
This message wasn't delivered to anyone because it's too large. The limit is 20 MB. This message is 25 MB.

Generating server: #550 5.3.4 SMTPSEND.OverAdvertisedSize; message size exceeds fixed maximum size ##

FYI: --> is Symantec Messaging Gateway (Brightmail email appliance running as VM).

Any help would be greatly appreciated.

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Senior IT System EngineerIT ProfessionalAsked:
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Senior IT System EngineerIT ProfessionalAuthor Commented:
Here's the settings on the HT-CAS servers:

Powershell Result
Do you have an option of breaking down the attachment in to two files of 10mb and then sending it across? if not, follow instructions on these two links....
Marwan OsmanCommented:
check the maximum message size on the device which has the role of sending emails out of your domain which is Brightmail email appliance in your case, it is cleared that it is configured to allow a maximum of 20 MB per attached.

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Senior IT System EngineerIT ProfessionalAuthor Commented:
Hi All,

The attachemnt is a PDF file and I also tried PPT file not compressed, so I don't know why Exchange told me it is larger than 20 MB ?

@Mario: What device ? it was sent through my laptop.
Marwan OsmanCommented:
what is the correct message size you are trying to send?
Marwan OsmanCommented:
I mean that the message is not denied from your exchange server, the Brightmail email appliance caused the issue and you need to check the message size limit on it, so please check out the below link to get help about the steps you need to follow to increase the message size limit on the appliance
Senior IT System EngineerIT ProfessionalAuthor Commented:
Ah yes,  How did you know if it was the Mail Gateway settings.

you are right: it is 20971520 bytes.

how come I didn't realize about that :-)

the actual file size is 18.3 MB (19,212,138 bytes) but for some reason it is still rejected.
Senior IT System EngineerIT ProfessionalAuthor Commented:
Does changethe limit / size can cause any unwanted outage ?
what is the size that I must match for both SYmantec and the Exchange  in the Screenshot below ?

Senior IT System EngineerIT ProfessionalAuthor Commented:
So what about the Transport Dumpster size ? do I need to change it into someother values ?
I don't have any DAG configured on both mailbox servers.
Marwan OsmanCommented:
Don't change other settings, change it to 30 MB in the symantec and wait for changes to be applied, leave it for 15 mins and try to send
Guy LidbetterCommented:
Hi There,

The attachment may well only be 18.3 MB (19,212,138 bytes), but the email itself will have a lot of overhead and metadata that it wraps everything up in, and it would easily push it over the limit.
Senior IT System EngineerIT ProfessionalAuthor Commented:
ok, so in this case I need to make it like the following:

"In/Outbound SMTP Configuration Maximum message size in bytes" in Symantec =  25 MB
"In/ExternalDsnMaxMessageAttachSize " in Exchange server = 20 MB

like 25 MB in total with added 5 MB as the buffer or inline attachment ?
Marwan OsmanCommented:
configure boss of them to 25 MB if you want to send 20 MB, or configure them to 30 MB if you want to be able to send 25 MB message, try this and inform if it does work successfuly or not
Senior IT System EngineerIT ProfessionalAuthor Commented:
ok, so if I configure that using powershell, do I need to restart or reboot anything ?
I wonder if it can be done during the business hours.
Marwan OsmanCommented:
it will be applied without restart
Senior IT System EngineerIT ProfessionalAuthor Commented:
What about the transport dumpster size ?

Since I do not have DAG configured somehow it is set as 50 MB from the default 18 MB by my predecessor would that limits the email size as well ?
Guy LidbetterCommented:
No it would not, no relation. However best practice says you should set it to a minimum of 1.5 times your max message size.
Senior IT System EngineerIT ProfessionalAuthor Commented:
Thanks !
Marwan OsmanCommented:
You are welcome Sir.
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