Mike Reed
asked on
SBS2008 POP3 Connector woes: attachments > 10MB are retrieved from POP3 svr, but not delivered to Exchange mailbox
Hi All,
I have spent many hours researching my POP3 Connector problem concerning attachments larger than 10MB not being delivered to their Exchange mailboxes.
Using EMC, I have:
a) set the Global Transport Settings "Maximum Receive Size" to 30000 (Org Config->Hub Transport->Global Settings)
b) set the only Send Connector's Maximum Message Size to 30MB (Org Config->Hub Transport->Send Connectors)
c) set ALL Receive Connectors "Maximum Message Size" to 30000 (Server Config->Hub Transport)
d) set the user's Mailbox SENDING *and* RECEIVING "Maximum Message Size" to 30000 (Recip Config->Mailbox)
e) restarted the "Microsoft Exchange Transport" service many times, as well as restarted the server itself.
If an email is sent to any of these POP3 Connector accounts with an attachment size that exceeds 10MB, the message is retrieved (and deleted) from the POP3 server, BUT the Exchange recipient receives nothing and the sender receives the NDR below:
Here's some more info from various shell commands:
GET-TRANSPORTSERVER | LIST
Notice lines 17 & 28 above? is it possible the External and InternalDsnMaxMessageAttac
Get-receiveconnector | List
The above lists all 3 Receive Connectors. From what I've read, only the "Windows SBS Fax Sharepoint Receive SBS2008" (starts at line 112 above) connector affects the POP3 Connector. But to play it safe, I set the "Maximum Message Size" to 30MB for all 3 connectors.
Lastly, here is the POP3 Connector log showing what appears to be a normal/successful retrieval for an email with a 15MB attachment (but it never makes it to recipient's mailbox):
It just boggles my mind that Microsoft can make what should be such a trivial task so enormously challenging :) But I guess it's job security for us IT folks :)
Thanks in advance,
-Mike
I have spent many hours researching my POP3 Connector problem concerning attachments larger than 10MB not being delivered to their Exchange mailboxes.
Using EMC, I have:
a) set the Global Transport Settings "Maximum Receive Size" to 30000 (Org Config->Hub Transport->Global Settings)
b) set the only Send Connector's Maximum Message Size to 30MB (Org Config->Hub Transport->Send Connectors)
c) set ALL Receive Connectors "Maximum Message Size" to 30000 (Server Config->Hub Transport)
d) set the user's Mailbox SENDING *and* RECEIVING "Maximum Message Size" to 30000 (Recip Config->Mailbox)
e) restarted the "Microsoft Exchange Transport" service many times, as well as restarted the server itself.
If an email is sent to any of these POP3 Connector accounts with an attachment size that exceeds 10MB, the message is retrieved (and deleted) from the POP3 server, BUT the Exchange recipient receives nothing and the sender receives the NDR below:
Delivery has failed to these recipients or distribution lists:
user@domain.com
This message exceeds the maximum message size allowed. Microsoft Exchange will not try to redeliver this message for you. Please make the message smaller -- by removing attachments, for example -- and try sending it again, or provide the following diagnostic text to your system administrator.
Diagnostic information for administrators:
Generating server: domain.local
Steve@domain.com
#< #5.2.3 smtp;550 5.2.3 RESOLVER.RST.SendSizeLimit; message too large for this sender> #SMTP#Here's some more info from various shell commands:
GET-TRANSPORTSERVER | LIST
Name : SBS2008
AntispamAgentsEnabled : True
ConnectivityLogEnabled : False
ConnectivityLogMaxAge : 30.00:00:00
ConnectivityLogMaxDirectorySize : 250MB
ConnectivityLogMaxFileSize : 10MB
ConnectivityLogPath : C:\Program Files\Microsoft\Exchange Server\TransportRoles\Logs\Connectivity
DelayNotificationTimeout : 04:00:00
ExternalDelayDsnEnabled : True
ExternalDNSAdapterEnabled : True
ExternalDNSAdapterGuid : 00000000-0000-0000-0000-000000000000
ExternalDNSProtocolOption : Any
ExternalDNSServers : {}
ExternalIPAddress :
ExternalDsnDefaultLanguage : en-US
ExternalDsnLanguageDetectionEnabled : True
ExternalDsnMaxMessageAttachSize : 10MB
ExternalDsnReportingAuthority : DomainName.local
ExternalDsnSendHtml : True
ExternalPostmasterAddress : postmaster@DomainName.com
InternalDelayDsnEnabled : True
InternalDNSAdapterEnabled : True
InternalDNSAdapterGuid : 00000000-0000-0000-0000-000000000000
InternalDNSProtocolOption : Any
InternalDNSServers : {}
InternalDsnDefaultLanguage : en-US
InternalDsnLanguageDetectionEnabled : True
InternalDsnMaxMessageAttachSize : 10MB
InternalDsnReportingAuthority : SBS2008.DomainName.local
InternalDsnSendHtml : True
MaxConcurrentMailboxDeliveries : 7
MaxConcurrentMailboxSubmissions : 20
MaxConnectionRatePerMinute : 1200
MaxOutboundConnections : 1000
MaxPerDomainOutboundConnections : 20
MessageExpirationTimeout : 2.00:00:00
MessageRetryInterval : 00:01:00
MessageTrackingLogEnabled : True
MessageTrackingLogMaxAge : 30.00:00:00
MessageTrackingLogMaxDirectorySize : 250MB
MessageTrackingLogMaxFileSize : 10MB
MessageTrackingLogPath : C:\Program Files\Microsoft\Exchange Server\TransportRoles\Logs\MessageTracking
MessageTrackingLogSubjectLoggingEnabled : True
OutboundConnectionFailureRetryInterval : 00:10:00
IntraOrgConnectorProtocolLoggingLevel : None
PickupDirectoryMaxHeaderSize : 64KB
PickupDirectoryMaxMessagesPerMinute : 100
PickupDirectoryMaxRecipientsPerMessage : 100
PickupDirectoryPath : C:\Program Files\Microsoft\Exchange Server\TransportRoles\Pickup
PipelineTracingEnabled : False
ContentConversionTracingEnabled : False
PipelineTracingPath : C:\Program Files\Microsoft\Exchange Server\TransportRoles\Logs\PipelineTracing
PipelineTracingSenderAddress :
PoisonMessageDetectionEnabled : True
PoisonThreshold : 2
QueueMaxIdleTime : 00:03:00
ReceiveProtocolLogMaxAge : 30.00:00:00
ReceiveProtocolLogMaxDirectorySize : 250MB
ReceiveProtocolLogMaxFileSize : 10MB
ReceiveProtocolLogPath : C:\Program Files\Microsoft\Exchange Server\TransportRoles\Logs\ProtocolLog
\SmtpReceive
RecipientValidationCacheEnabled : False
ReplayDirectoryPath : C:\Program Files\Microsoft\Exchange S
erver\TransportRoles\Replay
RootDropDirectoryPath : C:\inetpub\mailroot
RoutingTableLogMaxAge : 7.00:00:00
RoutingTableLogMaxDirectorySize : 50MB
RoutingTableLogPath : C:\Program Files\Microsoft\Exchange Server\TransportRoles\Logs\Routing
SendProtocolLogMaxAge : 30.00:00:00
SendProtocolLogMaxDirectorySize : 250MB
SendProtocolLogMaxFileSize : 10MB
SendProtocolLogPath : C:\Program Files\Microsoft\Exchange Server\TransportRoles\Logs\ProtocolLog
\SmtpSend
TransientFailureRetryCount : 6
TransientFailureRetryInterval : 00:05:00
AntispamUpdatesEnabled : False
InternalTransportCertificateThumbprint : AE2C4A8F115EA3B3AE8E65BF57244230E3404
538
IsValid : True
OriginatingServer : SBS2008.DomainName.local
ExchangeVersion : 0.1 (8.0.535.0)
DistinguishedName : CN=SBS2008,CN=Servers,CN=Exchange Adm
inistrative Group (FYDIBOHF23SPDLT),C
N=Administrative Groups,CN=First Orga
nization,CN=Microsoft Exchange,CN=Ser
vices,CN=Configuration,DC=DomainName,DC
=local
Identity : SBS2008
Guid : 6de46aca-7e0e-4147-9f6e-23e5f716d352
ObjectCategory : DomainName.local/Configuration/Schema/m
s-Exch-Exchange-Server
ObjectClass : {top, server, msExchExchangeServer}
WhenChanged : 8/15/2010 11:10:29 AM
WhenCreated : 8/13/2010 2:29:51 PMNotice lines 17 & 28 above? is it possible the External and InternalDsnMaxMessageAttac
Get-receiveconnector | List
AuthMechanism : Tls, Integrated, BasicAuth, BasicAuth
RequireTLS, ExchangeServer
Banner :
BinaryMimeEnabled : True
Bindings : {10.10.0.2:25}
ChunkingEnabled : True
DefaultDomain :
DeliveryStatusNotificationEnabled : True
EightBitMimeEnabled : True
DomainSecureEnabled : False
EnhancedStatusCodesEnabled : True
LongAddressesEnabled : False
OrarEnabled : False
Fqdn : SBS2008.DomainName.local
Comment :
Enabled : True
ConnectionTimeout : 00:10:00
ConnectionInactivityTimeout : 00:05:00
MessageRateLimit : unlimited
MaxInboundConnection : 5000
MaxInboundConnectionPerSource : unlimited
MaxInboundConnectionPercentagePerSource : 100
MaxHeaderSize : 64KB
MaxHopCount : 30
MaxLocalHopCount : 8
MaxLogonFailures : 3
MaxMessageSize : 30240KB
MaxProtocolErrors : 5
MaxRecipientsPerMessage : 5000
PermissionGroups : ExchangeUsers, ExchangeServers, Excha
ngeLegacyServers
PipeliningEnabled : True
ProtocolLoggingLevel : Verbose
RemoteIPRanges : {10.10.0.255-10.10.0.255, 10.10.0.0-1
0.10.0.253}
RequireEHLODomain : False
RequireTLS : False
EnableAuthGSSAPI : False
Server : SBS2008
SizeEnabled : EnabledWithoutValue
TarpitInterval : 00:00:05
AdminDisplayName :
ExchangeVersion : 0.1 (8.0.535.0)
Name : Default SBS2008
DistinguishedName : CN=Default SBS2008,CN=SMTP Receive Co
nnectors,CN=Protocols,CN=SBS2008,CN=S
ervers,CN=Exchange Administrative Gro
up (FYDIBOHF23SPDLT),CN=Administrativ
e Groups,CN=First Organization,CN=Mic
rosoft Exchange,CN=Services,CN=Config
uration,DC=DomainName,DC=local
Identity : SBS2008\Default SBS2008
Guid : 655686bf-95d8-4fee-bc09-00ed18c7b238
ObjectCategory : DomainName.local/Configuration/Schema/m
s-Exch-Smtp-Receive-Connector
ObjectClass : {top, msExchSmtpReceiveConnector}
WhenChanged : 9/10/2010 2:42:52 PM
WhenCreated : 8/13/2010 2:30:38 PM
OriginatingServer : SBS2008.DomainName.local
IsValid : True
AuthMechanism : BasicAuth
Banner :
BinaryMimeEnabled : True
Bindings : {127.0.0.1:25}
ChunkingEnabled : True
DefaultDomain :
DeliveryStatusNotificationEnabled : True
EightBitMimeEnabled : True
DomainSecureEnabled : False
EnhancedStatusCodesEnabled : True
LongAddressesEnabled : False
OrarEnabled : False
Fqdn : SBS2008.DomainName.local
Comment :
Enabled : True
ConnectionTimeout : 06:00:00
ConnectionInactivityTimeout : 00:05:00
MessageRateLimit : unlimited
MaxInboundConnection : 5000
MaxInboundConnectionPerSource : 20
MaxInboundConnectionPercentagePerSource : 2
MaxHeaderSize : 64KB
MaxHopCount : 30
MaxLocalHopCount : 8
MaxLogonFailures : 3
MaxMessageSize : 30240KB
MaxProtocolErrors : 5
MaxRecipientsPerMessage : 200
PermissionGroups : AnonymousUsers, ExchangeUsers
PipeliningEnabled : True
ProtocolLoggingLevel : Verbose
RemoteIPRanges : {127.0.0.1-127.0.0.1}
RequireEHLODomain : False
RequireTLS : False
EnableAuthGSSAPI : False
Server : SBS2008
SizeEnabled : Enabled
TarpitInterval : 00:00:05
AdminDisplayName :
ExchangeVersion : 0.1 (8.0.535.0)
Name : Windows SBS Fax Sharepoint Receive SB
S2008
DistinguishedName : CN=Windows SBS Fax Sharepoint Receive
SBS2008,CN=SMTP Receive Connectors,C
N=Protocols,CN=SBS2008,CN=Servers,CN=
Exchange Administrative Group (FYDIBO
HF23SPDLT),CN=Administrative Groups,C
N=First Organization,CN=Microsoft Exc
hange,CN=Services,CN=Configuration,DC
=DomainName,DC=local
Identity : SBS2008\Windows SBS Fax Sharepoint Re
ceive SBS2008
Guid : e037c39b-2caa-4dce-baff-182972d4a969
ObjectCategory : DomainName.local/Configuration/Schema/m
s-Exch-Smtp-Receive-Connector
ObjectClass : {top, msExchSmtpReceiveConnector}
WhenChanged : 9/10/2010 2:43:04 PM
WhenCreated : 8/13/2010 2:40:33 PM
OriginatingServer : SBS2008.DomainName.local
IsValid : True
AuthMechanism : Tls
Banner :
BinaryMimeEnabled : True
Bindings : {10.10.0.2:25}
ChunkingEnabled : True
DefaultDomain :
DeliveryStatusNotificationEnabled : True
EightBitMimeEnabled : True
DomainSecureEnabled : False
EnhancedStatusCodesEnabled : True
LongAddressesEnabled : False
OrarEnabled : False
Fqdn : remote.DomainName.com
Comment :
Enabled : True
ConnectionTimeout : 00:10:00
ConnectionInactivityTimeout : 00:01:00
MessageRateLimit : unlimited
MaxInboundConnection : 5000
MaxInboundConnectionPerSource : 20
MaxInboundConnectionPercentagePerSource : 2
MaxHeaderSize : 64KB
MaxHopCount : 30
MaxLocalHopCount : 8
MaxLogonFailures : 3
MaxMessageSize : 30240KB
MaxProtocolErrors : 5
MaxRecipientsPerMessage : 200
PermissionGroups : AnonymousUsers
PipeliningEnabled : True
ProtocolLoggingLevel : Verbose
RemoteIPRanges : {10.10.1.0-255.255.255.255, 10.10.0.2
54-10.10.0.254, 0.0.0.0-10.9.255.255}
RequireEHLODomain : False
RequireTLS : False
EnableAuthGSSAPI : False
Server : SBS2008
SizeEnabled : Enabled
TarpitInterval : 00:00:05
AdminDisplayName :
ExchangeVersion : 0.1 (8.0.535.0)
Name : Windows SBS Internet Receive SBS2008
DistinguishedName : CN=Windows SBS Internet Receive SBS20
08,CN=SMTP Receive Connectors,CN=Prot
ocols,CN=SBS2008,CN=Servers,CN=Exchan
ge Administrative Group (FYDIBOHF23SP
DLT),CN=Administrative Groups,CN=Firs
t Organization,CN=Microsoft Exchange,
CN=Services,CN=Configuration,DC=pasbj
erg,DC=local
Identity : SBS2008\Windows SBS Internet Receive
SBS2008
Guid : 7ad3ffc2-9acc-4c14-9d57-687a97a07d95
ObjectCategory : DomainName.local/Configuration/Schema/m
s-Exch-Smtp-Receive-Connector
ObjectClass : {top, msExchSmtpReceiveConnector}
WhenChanged : 9/10/2010 2:43:14 PM
WhenCreated : 8/15/2010 11:10:25 AM
OriginatingServer : SBS2008.DomainName.local
IsValid : TrueThe above lists all 3 Receive Connectors. From what I've read, only the "Windows SBS Fax Sharepoint Receive SBS2008" (starts at line 112 above) connector affects the POP3 Connector. But to play it safe, I set the "Maximum Message Size" to 30MB for all 3 connectors.
Lastly, here is the POP3 Connector log showing what appears to be a normal/successful retrieval for an email with a 15MB attachment (but it never makes it to recipient's mailbox):
[t 0] 09/11/10, 11:46:07: (AsyncConn[ pop.DomainName.com:110 ]) Connecting to 'pop.DomainName.com' on port 110.
[t 0] 09/11/10, 11:46:07: (POP3) [RX] +OK <24426.1284219967@p3pop01-09.prod.phx3.gdg>
[t 0] 09/11/10, 11:46:07: (POP3) [TX] USER steve@DomainName.com
[t 0] 09/11/10, 11:46:07: (POP3) [RX] +OK
[t 0] 09/11/10, 11:46:07: (POP3) [TX] PASS ************************
[t 0] 09/11/10, 11:46:07: (POP3) [RX] +OK
[t 0] 09/11/10, 11:46:07: (POP3) [TX] STAT
[t 0] 09/11/10, 11:46:07: (POP3) [RX] +OK 1 16013031
[t 0] 09/11/10, 11:46:07: Check for new messages: 1 (15.2 MB) total.
[t 0] 09/11/10, 11:46:07: (AsyncConn[ localhost:25 ]) Connecting to 'localhost' on port 25.
[t 0] 09/11/10, 11:46:07: (SMTP) [RX] 220 SBS2008.DomainName.local Microsoft ESMTP MAIL Service ready at Sat, 11 Sep 2010 11:46:06 -0400
[t 0] 09/11/10, 11:46:07: (SMTP) [TX] EHLO SBS2008
[t 0] 09/11/10, 11:46:07: (SMTP) [RX] 250-SBS2008.DomainName.local Hello [127.0.0.1]
[t 0] 09/11/10, 11:46:07: (SMTP) [RX] 250-SIZE 30965760
[t 0] 09/11/10, 11:46:07: (SMTP) [RX] 250-PIPELINING
[t 0] 09/11/10, 11:46:07: (SMTP) [RX] 250-DSN
[t 0] 09/11/10, 11:46:07: (SMTP) [RX] 250-ENHANCEDSTATUSCODES
[t 0] 09/11/10, 11:46:07: (SMTP) [RX] 250-AUTH LOGIN
[t 0] 09/11/10, 11:46:07: (SMTP) [RX] 250-8BITMIME
[t 0] 09/11/10, 11:46:07: (SMTP) [RX] 250-BINARYMIME
[t 0] 09/11/10, 11:46:07: (SMTP) [RX] 250 CHUNKING
[t 0] 09/11/10, 11:46:07: (POP3) [TX] LIST
[t 0] 09/11/10, 11:46:07: (POP3) [RX] +OK
[t 0] 09/11/10, 11:46:08: (POP3) [RX] 1 16013031
[t 0] 09/11/10, 11:46:08: (POP3) [RX] .
[t 0] 09/11/10, 11:46:08: Downloading message 1 of 1.
[t 0] 09/11/10, 11:46:08: (POP3) [TX] RETR 1
[t 0] 09/11/10, 11:46:11: (POP3) [RX] +OK 16013031 octets
[t 0] 09/11/10, 11:46:38: Sending message 1 to the SMTP recipient Steve@DomainName.com...
[t 0] 09/11/10, 11:46:38: (SMTP) [TX] MAIL FROM: <Mike@SendingDomainName.com> RET=FULL
[t 0] 09/11/10, 11:46:38: (SMTP) [RX] 250 2.1.0 Sender OK
[t 0] 09/11/10, 11:46:38: (SMTP) [TX] RCPT TO: <Steve@DomainName.com> NOTIFY=FAILURE
[t 0] 09/11/10, 11:46:38: (SMTP) [RX] 250 2.1.5 Recipient OK
[t 0] 09/11/10, 11:46:38: (SMTP) [TX] DATA
[t 0] 09/11/10, 11:46:38: (SMTP) [RX] 354 Start mail input; end with <CRLF>.<CRLF>
[t 0] 09/11/10, 11:46:38: (SMTP) [TX]
.
[t 0] 09/11/10, 11:46:42: (SMTP) [RX] 250 2.6.0 <ED4E451980F2AC4EA2FE427C69824B111E214A5AA2@SBS.compusolve.local> Queued mail for delivery
[t 0] 09/11/10, 11:46:42: (SMTP) [TX] QUIT
[t 0] 09/11/10, 11:46:42: Deleting message 1 of 1.
[t 0] 09/11/10, 11:46:42: (POP3) [TX] DELE 1
[t 0] 09/11/10, 11:46:42: (SMTP) [RX] 221 2.0.0 Service closing transmission channel
[t 0] 09/11/10, 11:46:42: (AsyncConn[ localhost:25 ]) Connection to 'localhost' closed.
[t 0] 09/11/10, 11:46:42: (POP3) [RX] +OK
[t 0] 09/11/10, 11:46:42: (POP3) [TX] QUIT
[t 0] 09/11/10, 11:46:42: (POP3) [RX] +OK
[t 0] 09/11/10, 11:46:42: (AsyncConn[ pop.DomainName.com:110 ]) Connection to 'pop.DomainName.com' closed.It just boggles my mind that Microsoft can make what should be such a trivial task so enormously challenging :) But I guess it's job security for us IT folks :)
Thanks in advance,
-Mike
ASKER
Thanks pvlier, but I've seen that article many times and triple checked my settings against it.
I believe all the shell commands that I logged in my original question, as well as my notes, would show that I have made all those settings. What other information would be helpful that you hinted at?
I believe all the shell commands that I logged in my original question, as well as my notes, would show that I have made all those settings. What other information would be helpful that you hinted at?
ASKER
The line below from the NDR that the sender receives really puzzles me. Why would it be a SendSizeLimit? And exactly who is the "sender" that this error message refers to? It certainly can't be the the original sender, as their email was successfully delivered to the ISP's POP3 server.
Is the "sender" the "pop3connector@domain" account that resides on the SBS box? It seems to be a hidden internal account that I have seen in some SBS log.
But boy this NDR sure does confuse the heck of of the original sender :(
#< #5.2.3 smtp;550 5.2.3 RESOLVER.RST.SendSizeLimit
Is the "sender" the "pop3connector@domain" account that resides on the SBS box? It seems to be a hidden internal account that I have seen in some SBS log.
But boy this NDR sure does confuse the heck of of the original sender :(
#< #5.2.3 smtp;550 5.2.3 RESOLVER.RST.SendSizeLimit
ASKER
Oops a typo. I meant to say:
But boy this NDR sure does confuse the heck out of the original sender :(
But boy this NDR sure does confuse the heck out of the original sender :(
ASKER CERTIFIED SOLUTION
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In my post were 2links... in the second link the solution was to configure the SEND size and not the RECEIVE size... but no worries here, glad you found out there was an overhead causing (more) confusion :-)
ASKER
That 2nd link's thread was very confusing, at best :) Early on it was suggested to increase the SEND limit. But after the OP indicated it was a receive error, it was suggested to increase the RECEIVE limit... Seems like one solution would be to blindly increase every limit one can find :)
In my many hours of researching this, I have never seen a crystal clear explanation of this particular issue with the POP3 Connector and the need to set the Maximum SEND size despite the fact that the initial problem is an inability to RECEIVE a message.
Microsoft has outdone themselves in making what should be a simple task, overly complicated and unintuitive. What else is new, right?
My hope is that my many hours of research and detailed explanation (above) will make it into the hands of the next poor IT person that runs into this mess.
End of saga :)
In my many hours of researching this, I have never seen a crystal clear explanation of this particular issue with the POP3 Connector and the need to set the Maximum SEND size despite the fact that the initial problem is an inability to RECEIVE a message.
Microsoft has outdone themselves in making what should be a simple task, overly complicated and unintuitive. What else is new, right?
My hope is that my many hours of research and detailed explanation (above) will make it into the hands of the next poor IT person that runs into this mess.
End of saga :)
ASKER
Ok, a little more clarification of why I think MSoft boggled this so badly:
My client wanted to be able to receive emails up to 30MB and send emails up to 15MB. So, using EMC I set the receive limits to 30000 and send limits to 15000 (ok, technically I did not set them to 30MB/15MB, but close enough). Seems logical, doesn't it?
The totally unintuitive part is that *any* SEND limit would affect the ability to *receive* via the POP3 Connector. MSoft needs to get this documented and make some adjustments within EMC and/or the POP3 Connector config tool.
So to play it safe, set *all* SEND limits under Org. Config->Hub Transport->Send Connectors<whatever name of your send connector is> and Org. Config->Hub Transport->Global Settings->Transport Settings to a value >= the largest message you want to allow. Then hope MSoft doesn't move all these freakin settings somewhere else in the next version of Exchange :)
My client wanted to be able to receive emails up to 30MB and send emails up to 15MB. So, using EMC I set the receive limits to 30000 and send limits to 15000 (ok, technically I did not set them to 30MB/15MB, but close enough). Seems logical, doesn't it?
The totally unintuitive part is that *any* SEND limit would affect the ability to *receive* via the POP3 Connector. MSoft needs to get this documented and make some adjustments within EMC and/or the POP3 Connector config tool.
So to play it safe, set *all* SEND limits under Org. Config->Hub Transport->Send Connectors<whatever name of your send connector is> and Org. Config->Hub Transport->Global Settings->Transport Settings to a value >= the largest message you want to allow. Then hope MSoft doesn't move all these freakin settings somewhere else in the next version of Exchange :)
http://exchangepedia.com/2007/09/exchange-server-2007-setting-message-size-limits.html
There has also been another thread here before: https://www.experts-exchange.com/questions/26244867/550-5-2-3-RESOLVER-RST-SendSizeLimit-message-too-large-for-this-sender-Original-message-headers.html. There is a screenshot that looks promising.