My Sendmail SMTP-relay experiencing problem as user sends email to over 70 users. the error message on sendmail log is (Sending error 421 4.7.0 Temporary System Problem), however the return fail message is (reason: 530 5.7.0 Must issue a STARTTLS command first).
About 60 users get the email out of 70, I don't know what is the problem. I browsed internet, some peole suggest to delay sending emails by 1000ms between each email. some other indcates the problem is with (using plain autentication). I basically don't know how to fix this:
Using following services:
SMTP-relay: installed on Linux system
user send email through SMTP-relay installed on the same server.
if you require other information please let me know.
your help is highly appreciated
When do you get this message?
If this is within PHP, why are you using the SMTP method within PHP versus using the direct injection method?
Do not define SMTP within php.ini but use sendmail_path=/usr/sbin/se
This will have PHP submitting the message to sendmail without the SMTP interaction.
This is similar to
echo "To: <emailaddress>
Subject: direct injection message
This is the message Body(message)
" | /usr/sbin/sendmail -oi -t
the -t tells sendmail to look for the destination of the message within the data TO, Cc and Bcc (Bcc will be stripped after processing.
If the error is within the sendmail log, a 4xx error means that sendmail will retry sending this message at a later time.
Double check what your queue lifetime is within sendmail, to make sure it is at least one day which means it will attempt to transmit messages to which it gets 4xx (temporary error) for the queue lifetime before giving up and treating the temporary error as a permanent one.