I run exim at work as our SMTP server. It supports TLS for using ssl when sending and receiving (if it converses with a mail client or other server that supports it).
I've educated the users about ticking the ssl option on their email clients, so emails are automatically encrypted at least to our mail server, and sometimes on the next hop too (I have spotted in the logs a few other servers talking via ssl to us).
This doesn't give you the same benefits of encrypting the message before you send. The mail is unencrypted when in the mail spool, there's no guarantee the hops'll all be encrypted, but it's a start at least - and if more servers do bring TLS facilities online, then you'll get encryption happening automatically without the users having to worry about it.
The original posting doesn't say if the server is running pop/imap, and thus if it is used as the final delivery point for those 10,000 users.
If it is, then the hashing of the mailbox path that lucky luck mentioned is worth investigating. Also worth investigating is alternative mailbox formats. If you're using mbox format, then I'm not surprised there's a problem if you have a large number of users (and/or reasonably large mailboxes).
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I run exim at work as our SMTP server. It supports TLS for using ssl when sending and receiving (if it converses with a mail client or other server that supports it).
I've educated the users about ticking the ssl option on their email clients, so emails are automatically encrypted at least to our mail server, and sometimes on the next hop too (I have spotted in the logs a few other servers talking via ssl to us).
This doesn't give you the same benefits of encrypting the message before you send. The mail is unencrypted when in the mail spool, there's no guarantee the hops'll all be encrypted, but it's a start at least - and if more servers do bring TLS facilities online, then you'll get encryption happening automatically without the users having to worry about it.
The original posting doesn't say if the server is running pop/imap, and thus if it is used as the final delivery point for those 10,000 users.
If it is, then the hashing of the mailbox path that lucky luck mentioned is worth investigating. Also worth investigating is alternative mailbox formats. If you're using mbox format, then I'm not surprised there's a problem if you have a large number of users (and/or reasonably large mailboxes).
There has been some discussion about these issues on the exim-users mailing list. I read it via egroups.