What does "Dictionary attack supression rejecting" means?
The following is shown at the message tracker:
 2020-05-07 09:49:38 (SMTP)<199073> [g->c] 450 Requested mail action not taken  2020-05-07 09:49:38 (SMTP)<199073> [c->g] RCPT TO:<email@example.com <mailto:firstname.lastname@example.org > >  2020-05-07 09:49:38 (SMTP)<199073> Dictionary attack supression rejecting address: email@example.com <mailto:firstname.lastname@example.org >
I can't find anything about this message, could someone tell me something about this?
the dictionary attack has the following "reason".
A dictionary attack is an attack where senders try to miss-use the mail-command to send in mails
For example if messages are send to "various words in a dictionary"@example.com at some point these messages are accepted as valid recipients as a valid mail-address might have been found randomly.
SMG is keeping track of "wrong commands/recipients". If a sender tries to send out messages to wrong, not RFC-valid recipients this brings up a dictionary attach.
In this example you posted the SMTP-Command used by the sender.
the command is not rfc valid and wrong. A corrected command for example should look like this:
RCPT TO:"username" <email@example.com>
The command tries to use the mailserver for relaying.
As the example recipient does not exist (example.com-domain)
SMG is "noticing this and bringing up the dictionary attack suppression.
A bit further on dictionary attack spam: