Linux – Why does Exim puts emails on hold if there are frozen messages in the queue

emaileximlinuxsmtp

I've a CentOS with CPanel server working as a SMTP server, which currently uses 20 different hostnames and IP addresses to deliver email for an email newsletter service.

However, it's extremely slow in sending emails. It's sending like 10 emails per minute, which I check by running the "exim -bpc" command. What could be affecting this?

One thing I'm supposing, is that there are frozen messages in the queue, which are slowing down the sending until they're sent out, and are putting new messages on hold.

What are the most common reasons a message can get frozen?

Also, would it be more efficient to use 20 different small VPSs to send out email rather than use one large VPS with the 20 different hostnames and IPs in it?

Best Answer

A frozen message is a message that cannot delivered nor bounced. You should not see many frozen messages, and besides, they should not affect performance at all. Are you running an open relay, by any chance? Otherwise it is probably a configuration issue (Do you accept mail? Do you bounce everything, even spam you (eventually) receive? )

A problem I have seen is that sometime you can get tarpitted, especially if you send "spammy" messages (I guess a newsletter could fit that description). In this case a single message will block the entire queue. How many queue runners do you use? You can try increase their number and see what happens. If you get tarpitted, do you have SPF and DKIM set up? They may help in this case.

Related Solutions

Exim: remote host is local host

Exim doesn't, by default, let you send mail back to yourself. You can change this behavior by using the self router option. Here's an example from my config in which I had to use self = send to get Exim to send "slow" mail to another instance on the same host:

stalemail:
  driver = manualroute
  condition = ${if > {$message_age}{900}{yes}{no}}
  self = send
  domains = ! +local_domains
  route_list = * mailhub-01.example.com::8025:mailhub-02.example.com::8025
  transport = remote_smtp

Exim speed up mails send/recieve mechanism

I did this the following way: I have setup a machine in London and China. I have setup mirror GlusterFS for /home were accounts are using Maildir (1 file per email) and it's configured with standard Virtualmin. This way, each email message is replicating from London to China upon delivery or deletion. LDAP is also replicated between sites (the user database). With GeoIP DNS, if I am in China, I download or send to my mail from China server and vice-versa by having the same settings. So this is a working way of doing this for 10.000+ mailboxes. This is not that difficult to setup and works well. With your configuration, you could setup a plain postfix server with virtualmin, which gives you all sort of virus and anti-spam scanning, and then you simply relay all mail to US. The authentication you can make yourself via https query to your CPANEL server, but I never did something like this.

Best Answer

Related Solutions

Exim: remote host is local host

Exim speed up mails send/recieve mechanism

Related Topic