My customer has dynamic distribution groups with large member counts (5000+ in some cases). In Exchange 2010 the tooltip for large audience appears with accurate numbers, however, 2013 mailboxes only see 1000 in the tooltip.
I've verified on the server that holds the arbitration mailbox:
[PS] C:\windows\system32>get-mailbox -Arbitration | where {$_.PersistedCapabilities -match "GMGen"} | Select Name, Database
that it is successfully logging group metrics gen start (MsExchange MailTips Event 14036) and completions (Event 14034).
\ProgramFiles\Microsoft\Exchange Server\V15\GroupMetrics shows the proper files and the groups are listed in the changedgroups.txt file.
However, checking the attribs on the DDG I see it apparently capped at 1000 users:
msExchGroupExternalMemberCount: 0;
msExchGroupMemberCount: 1000;
This looks suspiciously like the LDAP MaxPageSize limit, but I would expect Exchange is smart enough to be able to utilize multiple pages for request and responses.
In 2010 the metrics were stored on CAS, but now that 2013 stores it in AD, seems we're hitting a missed case bug? Or is there a config file somewhere that can be modified to allow GMGen to count groups with more than 1000 members?
-Steve