Re: monit SMTP

[Martin Pala]

Hi Michael,

my personal point of view:

1.) SMTP reliability (general):

SMTP uses message responsibility chain. In the case that server receives 
some message, it guarantees that it will be not lost until it will be 
delivered to the recipient or to the next hop. There are many 
possibilities in the case of failure how to report an error and/or 
return mail to the sender (for example delivery status notification). 
SMTP is reliable transfer, its problem is that it guarantees no delivery 
time. The chain is as strong as its weakest link. It is not usual that 
SMTP  client drops messages it should deliver in the case of error. 
Don't worry - TCP and UDP example is far away from this problem, 
mentioned Mozilla mail (or Outlook Express if you'd like to) is adequate 
example.


2.) I like to be notified that something happened with systems which i'm 
responsible for, SMS gateway with SMTP interface is superior tool. It is 
no problem for me if i will receive the alerts delayed, but it is bad 
for me when i will receive only subset or none of alerts in the case of 
temporary error. Sure - this is not cure-all and another paralel backup 
methods needs to be used to watch the system and handle alerts.


3.) I agree that the code should be clear, simple and modular. However i 
see no problem in using threads in the case that it makes sense. Threads 
are not the evil - like with everything in the life, you need to learn 
it and its pitfalls. Generaly in the case that some error is found, i 
will try to fix it - problems are here for being solved.


4.) syslog is very important (maybe you will be surprised that it it 
works via TCP too - for example syslog-ng), but it provides no advantage 
if you need to deliver alert for example via SMS - in such case it will 
involve more processes to deliver the message, thus it is more error prone.


5.) inlined SMTP implementation with message queue is still the most 
reliable solution for me. In the case that i will have time, i will look 
on it


Cheers,
Martin

Btw. i'm wondering that you are using Sendmail and talking about security