Hi Willy
mybe something like this could work:
1) save the whole string in faults_old
2) check if >0 and if sLast10errors not equal to faults_old
(not tested)
if ((((split ' ',ReadingsVal("Mythz","sLast10errors",0))[1]) > 0) and (ReadingsVal("Mythz","sLast10errors",0) ne ReadingsVal("Mythz","faults_old",0)) { DebianMail('xxxxx@t-online.de','Tecalor Mythz Alarm - ERROR','Fehlermeldung: '. $EVENT,'/mnt/fhem/Tecalor-Fehlermeldungen.txt'); fhem("setreading Mythz faults_old ". (ReadingsVal("Mythz","sLast10errors",0)));
immi