Business mail servers on Linux: Exim, Dovecot and deliverability

Email feels like a given until it stops arriving. A poorly configured mail server sends your quotes to spam, blocks legitimate attachments or loses messages during a rushed migration. We configure and manage mail servers on Linux with Exim and Dovecot, focusing on the one thing that really matters: that your email leaves, lands in the inbox and stays yours. Documented configurations, a single point of contact, no lock-in tying you to us.

Overview

We handle business email end to end: choosing between a dedicated server and a managed solution, configuring Exim for sending and receiving and Dovecot for IMAP and POP3, domain authentication, anti-spam and migrating existing mailboxes. The focus is deliverability: convincing Gmail, Outlook and the other major providers that your messages are legitimate, and keeping it that way over time.

The difference from an improvised setup shows up later. A domain’s reputation takes months to build and an afternoon to burn: that’s why we read the DMARC reports, keep an eye on blacklists and only touch the configuration through tracked changes. We leave you DNS records explained line by line, mailboxes you administer yourself, and a system that anyone - after us - can understand and maintain.

Typical problems we solve

• Business email lands in spam on Gmail and Outlook → we fix and align SPF, DKIM and DMARC and check the reputation of the sending IP.
• Someone is using your domain for phishing without your knowledge → we turn on DMARC with reporting, read the reports and shut down whoever is sending in your name.
• A compromised mailbox is sending spam and the IP lands on a blacklist → we stop the abuse, rotate credentials and follow through on delisting.
• Migrating from the old provider is scary because no one wants to lose the archive → we sync over IMAP and move the MX records only once the copy is verified.
• Transactional email from your management software or e-commerce store isn’t arriving → we separate the flows, authenticate sending and test real-world delivery.
• Anti-spam is blocking genuine customers along with the spam → we tune Rspamd with scores, whitelists and greylisting calibrated to your traffic.
• The mail server is a black box configured years ago → we document it, update TLS and authentication and bring it back under control.

What’s included

• Mail server setup: Exim for SMTP and Dovecot for IMAP and POP3, with mailboxes, aliases, forwards and quotas across one or more domains.
• Deliverability: SPF, DKIM and DMARC records configured and aligned, IP reputation monitoring and delivery tests to the major providers.
• Anti-spam and anti-abuse: filtering with Rspamd or SpamAssassin, greylisting, rate limiting and rules that stop outbound spam before it burns your reputation.
• TLS everywhere: encryption on sending and receiving with Let’s Encrypt certificates, up-to-date ciphers and configuration that meets modern provider policies.
• Email migration: mailbox inventory, IMAP sync without losing messages and a planned MX cutover, with rollback ready.
• Domain and mailbox management: creation, quotas, mail backups and Roundcube webmail when you need browser access.
• Documentation and autonomy: DNS records explained, written procedures and credentials in your hands, so you administer mailboxes without depending on us.

Stack and technologies

SMTP transport runs on Exim, mailbox access on Dovecot, with Maildir storage and virtual accounts on file or database depending on scale. Anti-spam is Rspamd in most cases - outbound DKIM signing, inbound verification, greylisting and scores tuned to real traffic - with SpamAssassin where it’s already in use. Domain authentication runs on SPF, DKIM and DMARC, with DMARC reports collected and interpreted to find out who’s sending in your name. TLS with Let’s Encrypt certificates encrypts every connection, and for browser access we integrate Roundcube. Servers run on Debian and Ubuntu - on request AlmaLinux, Rocky Linux or other distributions - hosted on Google Cloud as the first choice, on AWS or DigitalOcean as an alternative, or on your current provider. If running your own server doesn’t make sense, we set up managed solutions with the same care over DNS records.

A real-world example

A technical firm contacted us because the quotes they sent by email were going unanswered: many clients, almost all on Microsoft 365, couldn’t even find them in the spam folder. The audit found an SPF record broken by a newsletter service added years earlier, no DKIM signature, and the server’s IP listed on a minor blacklist. We fixed and aligned SPF, turned on DKIM signing in Exim, published a DMARC policy in monitoring mode and requested delisting, then verified delivery with test mailboxes at the major providers. Over the following weeks the DMARC reports confirmed that legitimate sends were aligned and surfaced an abusive sender, which we blocked by tightening the policy. Today the firm knows its quotes arrive, and has a documentation page that explains every record in its DNS.

Who it’s for

• SMEs and professional firms that want email on their own domain without messages scattered in spam.
• Agencies and software houses that manage domains and mailboxes for clients and want a repeatable, documented setup.
• Anyone sending transactional email or newsletters from management software, e-commerce or applications who’s running into delivery problems.
• Teams that need to migrate from an old server or provider without giving up years of archived mail.

How we work

The first step is an audit of DNS, mailboxes and reputation, which produces a readable picture: what’s broken, what’s at risk and what it costs to fix. Then we decide together between a dedicated server and a managed solution, without steering you toward whichever is more convenient for us. We configure things, fix deliverability and verify it with delivery tests against real providers, not just online validators. Migrations follow an agreed window: sync first, MX records after, rollback always ready. We cover Monday to Friday, 10:00-18:00: blocked mail is a P1, picked up within one business hour as described on the response times page. For ongoing management, hour packages never expire.