Move the %mail header generation and the sendmail part outside the fetch loop. Inside the loop, just say

     $mail{'Message'} .= <<EREC;
PROJECT: $SYS SEVERITY:

$REMTYPE

TODAYS DATE: $CURDATE

TECH: $OWNER

DATE: $DT TIME: $TM

STATUS: $TRSTAT SERVER: $SSYS

SUMMARY:

$DES

RESOLUTION:

$RESOLUTION

-------------------------------------------------------------------

EREC
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as the "concatenate" in your title suggests.