Emails are getting bounced back with my hosting saying ... Remote host said: 451 109.203.96.12 - You have been greylisted, please try later It looks like the mail servers of the hosting company are greylisted and thus affecting any cleints hosted on the same mail server IP. Has anyone come across this type of issue and any suggestions to fix? Thanks Gordano
It's got nothing to do with your hosts email server. Greylisting is an old, but still extremely effective, anti-spam system running on the email server you are attempting to send emails to....all our email servers run greylisting too. Greylisting uses a combination of incoming IP address, incoming "from" address, and the "to" address. The first time an email is sent from this unique combination, the email server rejects the email for a period of time (specified by the incoming email server administrator e.g. 180 seconds). Any properly configured sending email server will re-queue the outgoing email and attempt to re-send it at a future time. After a certain period of time has passed, and that unique combination of IP, from and to, attempts to deliver the email again, the incoming email server will accept the email, and that combination of factors will be stored on the greylisting DB for another period of time e.g. 36 days, and all future email will be accepted. If no email is delivered from that combination of factors (IP, to and from addresses) before the database record times-out, then new emails will need to go through the greylisting process again...deliver - delay - delivery accepted. There's nothing you can do to get around greylisting as it isn't in the power of your host to do anything about it - it's the receiving email server that does this. All you can do is... 1. Make sure you sending email server is properly configured to re-send emails for a period of time 2. Set up your sending email server only to send rejection messages to the sender if their message has been delayed by more than, say, 10 minutes. This will stop most senders receiving the greylisting message - as long as the email server is set-up to attempt to re-send a queued email before that 10 minutes is up. 3. Ask the receiving email address to whitelist your address (if they can) so all your future emails by-pass the greylisting filter. The thinking behind greylisting is that most spam emails are mass emails designed to quick delivery, and most spammers don't re-queue rejected emails, so by rejecting the initial email that will stop a lot of spam. As I said, it is a very old system, but it still works in a LOT of cases. Most greylisting time-outs are 1-3 minutes, so it's only delaying the first email from that IP, to and from address combination, by a few minutes at most.