Ahah, sigh (Tiscali smtp internal relay sucks)


beepbeep:~ zen$ telnet smtp.tiscali.it 25
Trying 213.205.33.13...
Connected to smtp.tiscali.it.
Escape character is '^]'.
421 averell.tiscali.it Service not available - too many connections

beepbeep:~ zen$ telnet smtp.tiscali.it 25
Trying 213.205.33.13...
Connected to smtp.tiscali.it.
Escape character is '^]'.
220 joe.tiscali.it ESMTP Service (7.3.122) ready

That is, the smtp relay for the entire tiscali network in Italy is a load balancer with ip address 213.205.33.13, which balances over two hosts

  • averell.tiscali.it has address 213.205.33.55
  • joe.tiscali.it has address 213.205.33.54

Anyway, it looks like the balancer has been configured with a dumb round robin (and with limits greater than those configured on the backend hosts). Please note that I’m connecting always from the same IP.
Net result: the balancer is useless. Half of the connections to the service get reset because of a single overloaded host. An innovative way to rate-limit the use of a service.

I’m writing this post waiting for my mails to get through.
Being sick and locked inside home makes me aggressive, did you notice?

Author: zen

Geek of all trades, having fun with *NIX, the Internet and computer security since 1995.

4 thoughts on “Ahah, sigh (Tiscali smtp internal relay sucks)”

  1. Vuol dire che per risparmiare banda, Tiscali limita l’uso del suo smtp, mentre altri limitano il P2P come Infostrada ecc. Tiscali ti fa usare il suo Smtp con parsimonia e se sumeri un certo limite di quantit  mail sui suoi server ti stoppa con i classici arcaici messaggi del protocollo smtp.
    Pare che si possa risolvere cambiando la dimensione dell’mtu da 1500 a 1490 o viceversa sul proprio router dsl o direttamente sul tcp della macchina con Sw tipo doctortcp ecc Da usare con massima cautela!

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