Sender-ID or Sender-ID Framework (SDIF) is an experimental protocol designed to allow any SMTP Server to validate the fact that the domain used in the incoming mails is legally used and approved by the real owner of such domain. By using records similar to the ones used by SPF, an SMTP Server may obtain detailed information about the authorized servers that are allowed to that domain name. Continue reading
Network configuration on Linux CentOS 5 is achieved through modifications on the following files: Continue reading
The actual definition of SMTP mail protocol allows explicitly for any entity to identify itself with any domain in both the HELO/EHLO and MAIL commands, it also allows any entity to identify itself with any mailbox in the From Header as long the syntax of RFC 2821 and 2822 is respected. This gives an attacker an opportunity to send mail pretending to be someone else, injecting thousands and even millions of unwanted mail into a normal mail flow. To minimize this risk and to make sure that the MTA server sending the mail is actually authorized to use the that domain, a new protocol was generated called Sender Policy Framework (SPF) which is one of the many tools that exist to fight against mail usage abuse. Continue reading
There are several factors when it comes to determine precisely the legitimate of a mail and the source. RFC’s 5585, 5863 and 4871 define the DomainKeys Identified Mail (DKIM) protocol in order to make this process easier.
The official DKIM definition is:
Changing password for user: admin
[root@IMSVA-1 ~]# /opt/trend/imss/PostgreSQL/bin/psql imss sa -c “update tb_administrator set md5_digest=′f859fc47dd1efd1a2b131344106cbab9′ where admin_name=′admin′;”
After this change, the password will be de default “imsva8.0” (without the quotes)
When you impose a size limitation in the mails your organization can receive or send you will notice that if you send a mail within this limit your mail will certainly be rejected. For example, supose you have size limit of 10MB and you send an attachment of 9.5MB, this mail will certainly be rejected, but why? Continue reading
You may have need to erase some character when sending a mail from the command line (specially in Windows CMD) because of any kind of mistake, but instead of making the correction you realize an error code shows up.
The reason for this is that in SMTP you can only transfer a very limited US-ASCII charset. Any other unrecognized character will not be recognized by the SMTP Server. When you press the “Back” key to correct you rmistake, what you are really doing is sending the corresponding ASCII code for that key and this is why your command ends up with an error code. Continue reading
There is always a time limit a mail can remain queued before deletion, no matter what the reason for the queuing is.
This time is defined by each mail server and in some cases it can be easily configured. For example: Postfix determines this behavior by checking the following parameter in main.cf
[root@cent01 mail]# postconf maximal_queue_lifetime
maximal_queue_lifetime = 5d Continue reading