MAX Query returns set results when using dbmail
You have at least one from eiwdata..eiwtcontentreceived (nolock) too many. You are fetching the max value for each row in eiwdata..eiwtcontentreceived. 

SET @tableHTML16 =
    N'&lt;H1&gt;BDI Feeds Last Received Batch&lt;/H1&gt;' +
    N'&lt;table border="1"&gt;' +                          -- close &lt;/tr&gt; here
    N'&lt;tr&gt;&lt;th&gt;Cerner&lt;/th&gt;&lt;th&gt;CPACS&lt;/th&gt;&lt;th&gt;DSCH123&lt;/th&gt;&lt;/tr&gt;' +
    CAST  ((SELECT   td = (select max(CPProcessedDateTime) from eiwdata..eiwtcontentreceived (nolock) where CapturePointDesc='OneC_Cerner_BDI:OCBDI1'), '',
                     td = (select max(CPProcessedDateTime) from eiwdata..eiwtcontentreceived (nolock) where CapturePointDesc='OneC_CPACS_BDI:OCBDI1'), '',
                     td = (select max(CPProcessedDateTime) from eiwdata..eiwtcontentreceived (nolock) where CapturePointDesc='OneC_DSCH123_BDI:OCBDI1'), ''

/*
             This table reference should be removed
             from eiwdata..eiwtcontentreceived (nolock)
*/    

        FOR XML PATH('tr'), TYPE
    ) AS NVARCHAR(MAX) ) +
    N'&lt;/table&gt;' ;