Έλεγχος για rotation log αρχείου

[Christos Ricudis]

George Notaras wrote:
> Το πρόβλημα είναι ότι ένας blacklisted smtpd δεν μπορεί να στείλει ούτε
> legitimate email για όσο χρόνο η IP του βρισκεται στο blacklist.

Greylisting legetai ayto poy 8eleis. Psakse sto google gia postfix 
greylisting, eixa brei 1-2 poly kala paketa gi ayth th douleia.

Synoptika, to greylisting leitourgei ws ekshs :

Ean enas SMTP sender parei ena 5XX error, einai ypoxrewmenos na 8ewrhsei 
oti h apostolh tou email apetyxe oristika.

Ean parei ena 4XX error, einai ypoxrewmenos na to 8ewrhsei ws proswrinh 
apotyxia kai na ksanaprospa8hsei se p.x. 5 lepta.

Oi spammers spaniws kanoyn ton kopo na ylopoihsoun to deytero kommati, 
giati apla den tous noiazei to reliability - tous noiazei h mazikothta.

To greylisting ekmetalleyetai ayth akribws th symperifora. Thn prwth 
fora poy 8a er8ei email gia ena sygkekrimeno recipient, trwei sth mapa 
ena 4XX error. O legitimate SMTP sender ksanastelnei to mynhma meta apo 
ena xroniko diasthma, opote esy (th deyterh fora) to dexesai. O spammer 
apla den ksanaprospa8ei.

Pleonekthmata :

1) Leitourgei akoma arketa apotelsmatika.  Ayto bebaia 8a stamathsei 
molis arxisoun na to kanoyn oloi, opote kai oi spammers apla 8a kanoyn 
dyo prospa8eies :)

2) Einai aplo lito kai eksypno.

Meionekthmata :

1) Eisagei anagkastika ena synh8ws mikro alla aprosdioristo delay sthn 
lhpsh *ka8e* email. O sender poy pairnei ena 4xx error einai men 
ypoxrewmenos na ksanaprospa8hsei na steilei to mail, alla kaneis den tou 
leei an ypoxreoutai na to kanei se 5 lepta h se 5 wres.

2) Yparxoun legitimate SMTP senders poy apotygxanoun oristika thn 
apostolh aokma kai me 4XX transient errors. Oi perissoteroi greylisting 
daemons exoun epiloges gia na tous "filtraroun", alla panta yparxei h 
periptwsh na xaseis kapoio mail.