The following companies/people offer consulting services for Dovecot:
Dovecot Solutions Oy - Dovecot support & development services
Heinlein Support GmbH - Dovecot, Postfix: mailserver consulting & training since 1992, author of several books about SMTP/IMAP (German/English)
state of mind - Fully-Featured Mailsystems and Groupwares relying on Dovecot as well as Anti-Virus and Anti-Spam-Gateways. We speak German and English.
Nci GmbH - Mailsystems on Dovecot/Postfix Antivirus and Spamgateways. Server Housing, Isp Munich, German and English.
iRedMail Project - Free, open source mail server solution, uses Dovecot as POP3/IMAP server. Works on Red Hat, CentOS, Debian, Ubuntu, OpenSuSE, FreeBSD.
Yukthi Systems - Email servers with spam, virus filtering; email archival; Groupware; Mobile phone integration. Postfix, Dovecot, etc. Remote server management.
Yaco Sistemas SL - Full Email server solutions with Dovecot as base, with spam, virus filtering; email archival; SquirrelMail customizations; Intranet Web and CMS systems with uniq login system.
Ardeek SRL - Dedicated email provider, onsite and outsourced HA solutions. Software integration services and professional services. Italian and english.
Apsis S.r.l. - Consultancy for hi availability email infrastructures based on opensource software.
ThisHosting.Rocks Support - A 24/7 Technical Support Team for Dovecot and other Linux-based software. Contact them for more info.