# Servolutions

> Servolutions IP Corporation ("Servolutions") makes email infrastructure software for Microsoft Exchange Server and Outlook: POP3/IMAP connectors, SMTP routing, and Outlook tools built for IT professionals. Products are licensed per server with no per-user fees; free 30-day trials require no registration.

Website: https://www.servolutions.com (English) — German site: https://www.servolutions.de

Full page text of this site (every product, download, requirements, help and knowledge-base page as plain text): https://www.servolutions.com/llms-full.txt

## Products

- [POPcon](https://www.servolutions.com/popcon): Windows service that connects Exchange Server to POP3 and IMAP mailboxes and distributes the downloaded mail to the right Exchange mailboxes automatically; TLS encryption; per-server license.
- [POPcon PRO](https://www.servolutions.com/popcon-pro): Everything in POPcon plus built-in antivirus, antispam filtering, rule-based distribution and mail archiving; parallel downloads for high-volume Exchange environments.
- [MultiSendcon](https://www.servolutions.com/multisendcon): Routes outgoing Exchange email through different SMTP relay servers (multiple send connectors / smart hosts) based on the sender address; per-sender authentication, TLS, unlimited routing rules; one-time license.
- [ChangeSender](https://www.servolutions.com/changesender): Exchange add-in that lets Outlook users choose the sender address for each outgoing message; automatic reply matching, signature switching, keyboard shortcuts.
- [AddressView for Outlook](https://www.servolutions.com/addressview): Shows the actual recipient email address in the Outlook inbox instead of only the display name; Outlook for Windows.
- [MailSync Hub](https://www.servolutions.com/mailsynchub): Cloud-based IMAP sync for Microsoft 365 and Exchange Online with OAuth 2.0 modern authentication; SaaS, under development.

## Downloads and pricing

- [Downloads](https://www.servolutions.com/download): Free 30-day trials of POPcon, POPcon PRO, MultiSendcon and ChangeSender; the trial converts to the full version when a license is entered.
- [Pricing](https://www.servolutions.com/pricing)

## Guides

- [Exchange mail flow guides](https://www.servolutions.com/guides): Answer-first guides for Exchange administrators on POP3/IMAP retrieval into Exchange, send connectors and smart hosts, sender addresses in Outlook, and OAuth2 for Microsoft 365 and Gmail; one guide is added at a time.
- [Does Exchange Server have a built-in POP3 connector?](https://www.servolutions.com/guides/exchange-pop3-connector-built-in): No — Exchange 2013–2019 and SE ship a POP3 client-access service, not a connector that fetches provider mailboxes; only SBS 2008/2011 had one; what replaces it.
- [The SBS 2008/2011 POP3 Connector: what it did, its limits, and the replacement](https://www.servolutions.com/guides/sbs-pop3-connector-replacement): The SBS console feature that pulled provider POP3 mailboxes into Exchange, compared row by row with a current POP3/IMAP connector (mapping, protocols, OAuth2, size limit, schedule), plus the migration steps when leaving SBS for Exchange 2016 to SE.
- [How to download POP3 and IMAP mailboxes into Exchange Server 2016, 2019 and SE](https://www.servolutions.com/guides/download-pop3-imap-into-exchange): Four steps — accepted domain, Default Frontend receive connector (size limit, anonymous users, scoping), connector service with POP3/IMAP accounts (ports 110/995/143/993, catch-all vs single-user, OAuth2 for Microsoft 365 and Gmail), first test — and a symptom table for 550 5.7.1, 530 5.7.1, port 25 and postmaster errors.
- [Catch-all (multidrop) mailbox vs one POP3 mailbox per user](https://www.servolutions.com/guides/catch-all-mailbox-vs-individual-pop3): A catch-all mailbox collects all mail for a domain in one POP3 account and the connector routes by recipient headers (To, CC, X-Original-To, Delivered-To, X-RCPT-TO, X-Envelope-To, Received; X-FORWARDED-FOR in POPcon PRO 4.6.2); individual mailboxes route exactly but cost one account per user. Comparison table, why BCC and mailing-list mail fails when providers strip headers, accepted recipient domains, postmaster and re-route address, recommendation: individual mailboxes where affordable, catch-all only with a provider that adds a delivery header.
- [Exchange send connectors route by recipient domain, not sender — how to route outbound mail by sender address anyway](https://www.servolutions.com/guides/exchange-send-connector-by-sender): An Exchange Server send connector is selected by address space (recipient domain), cost and scope, never by the sender; two connectors with the address space * split mail by cost, not by domain, and mail flow rules cannot pick a smart host on-premises. The three working options: separate AD sites with scoped connectors, a custom transport agent, or a sender-routing relay (MultiSendcon: one send connector to 127.0.0.1:2500, relay accounts with sender masks, per-sender credentials and TLS, fixed-sender replacement for empty-sender NDRs). Exchange Online has the condition natively.
- [Multiple smart hosts in Exchange 2016/2019: per recipient domain (built in) and per sender (with a relay)](https://www.servolutions.com/guides/exchange-multiple-smart-hosts): Exchange supports several smart hosts natively only by recipient domain — one send connector per destination address space; the most specific address space wins, then cost. Step-by-step for the native setup (EAC and New-SendConnector) and for per-sender routing through one connector to MultiSendcon on port 2500, with a comparison table.
- [Using IONOS, Strato or GMX as the smart host for Exchange: why the sender must match the login](https://www.servolutions.com/guides/ionos-strato-gmx-smart-host-exchange): IONOS accepts a message through its outgoing servers only when the sender domain equals the login mailbox domain and rejects empty senders (since January 2024); one Exchange login per sender domain via a relay fixes both.
- [Exchange: "A matching connector cannot be found to route the external recipient" — causes and fix](https://www.servolutions.com/guides/exchange-no-matching-send-connector): Exchange puts a message into the Unreachable queue with this error when no enabled send connector visible from the sending server's Active Directory site has an address space covering the recipient domain; causes table, Get-SendConnector check, Retry-Queue -Resubmit.
- [How Outlook users can choose a different From address on Exchange on-premises](https://www.servolutions.com/guides/outlook-choose-from-address-exchange): Outlook sends from the primary SMTP address unless the user has Send As or Send on Behalf on another mailbox or group; Exchange Server has no send-from-alias setting (SendFromAliasEnabled is Exchange Online only). Compares Send As, Send on Behalf, a shared mailbox and an Outlook add-in (ChangeSender).
- [Basic authentication is gone: fetching a Microsoft 365 mailbox by IMAP or POP3 with OAuth2 into Exchange](https://www.servolutions.com/guides/oauth2-pop3-imap-microsoft-365): Exchange Online refuses username/password for IMAP and POP3 in every tenant; a connector service signs in once with a Microsoft account, stores a refresh token and fetches with XOAUTH2. Seven setup steps for POPcon (IMAP, outlook.office365.com, 993, OAuth2 Microsoft), symptoms table, tenant consent settings.
- [Fetching Gmail and Google Workspace mail into Exchange over IMAP with OAuth2](https://www.servolutions.com/guides/gmail-oauth2-imap-into-exchange): Google Workspace refuses username/password sign-ins from third-party apps since 1 May 2025 and requires OAuth; personal Gmail is steered the same way and app passwords are "not recommended". Eight setup steps for POPcon (IMAP, imap.gmail.com, 993, OAuth2 Google, unverified-app warning), Workspace vs personal table, IMAP vs POP3 at Google, symptoms table.
- [Send As vs Send on Behalf vs sending from an alias](https://www.servolutions.com/guides/send-as-vs-send-on-behalf-vs-alias): Definitions of the three terms with what the recipient sees, where each is granted and where replies land; Send As and Send on Behalf are delegate permissions on another mailbox or group (Exchange Server and Exchange Online), sending from an alias is a tenant setting (SendFromAliasEnabled, default off, Exchange Online only) and does not exist on Exchange Server; the reply trap (Outlook on the web replies from the alias, Outlook desktop from the primary address) and where an Outlook add-in (ChangeSender) comes in.
- [POP3 or IMAP for retrieving provider mailboxes into Exchange? Ports, TLS, leave-on-server and OAuth2](https://www.servolutions.com/guides/pop3-vs-imap-for-exchange-retrieval): For a connector that empties a provider mailbox into Exchange both protocols deliver the same messages; the choice follows what the provider allows (Microsoft 365 and Gmail: IMAP on 993 with OAuth2), whether other clients read the mailbox, and the port conventions — 995 for POP3 over TLS, 993 for IMAP over TLS, STARTTLS on 110/143; delete / leave-on-server is a per-account setting for either protocol.
- [Exchange SMTP error codes explained: 421 4.4.1, 421 4.4.2, 451 4.7.0, 452 4.3.1, 530 5.7.1, 550 5.7.1 and more](https://www.servolutions.com/guides/exchange-smtp-error-codes): Exchange answers every SMTP submission with a reply code and an enhanced status code — 4.x.x means try again later, 5.x.x means rejected (RFC 3463, per Microsoft). One table per class for the replies a connector sees when submitting to Exchange (connection timed out, message submission rate, PRX, insufficient system resources / back pressure, need Rcpt, unrecognized authentication type, STARTTLS, client was not authenticated, user unknown, unable to relay, header size, no valid recipients): meaning, cause, fix, Set-ReceiveConnector commands, BADMAIL/PICKUP retry.
- ["550 5.7.1 Unable to relay" when a connector submits to Exchange: accepted domains and receive connector permissions](https://www.servolutions.com/guides/exchange-unable-to-relay-receive-connector): Exchange answers 550 5.7.1 Unable to relay when a session without relay permission (ms-Exch-SMTP-Accept-Any-Recipient) names a recipient outside the accepted domains. For a POP3/IMAP connector delivering to local mailboxes the fix is the missing accepted domain; hosts that must relay to external recipients get a dedicated receive connector as Microsoft describes.
- [POP3 retrieval or MX record to Exchange: when a connector is the right choice and when it is not](https://www.servolutions.com/guides/pop3-retrieval-vs-mx-record-exchange): Direct SMTP delivery needs an MX record in public DNS that resolves to the internet-facing server, inbound port 25 and your own spam filtering; a POP3/IMAP connector needs nothing inbound, leaves the MX record with the provider and keeps mail at the provider while Exchange is down. Comparison table, migration order, FAQ.
- [Where to install a POP3/IMAP connector: on the Exchange server, a member server, or a workstation](https://www.servolutions.com/guides/where-to-install-pop3-connector): A POP3/IMAP connector needs only outbound access to the provider's POP3/IMAP ports and SMTP access to one Exchange receive connector, so it runs on the Exchange server, another Windows Server or a Windows 10/11 PC (POPcon: Windows Server 2012-2025, Windows 7-11). Placement decides the port-25 path, whether the receive connector's remote IP ranges include the machine (Default Frontend accepts anonymous SMTP from all addresses by default, per Microsoft), and antivirus exclusions (POPcon program folder; Microsoft's Exchange exclusion list on the Exchange server). Seven checks for "downloads fine but cannot reach Exchange", how to move the connector (popcon.config + UIDS_*.dat).
- [Exchange Server SE (Subscription Edition) and POP3/IMAP mailbox retrieval: what changes, what does not](https://www.servolutions.com/guides/exchange-server-se-pop3-imap-retrieval): Exchange Server SE keeps the Exchange 2019 mail-flow model (receive connectors, send connectors, accepted domains) and has no built-in POP3 connector; Microsoft describes SE RTM as code equivalent to Exchange Server 2019 CU15 except licence agreement, product name and build number. In-place upgrade only from 2019 CU14/CU15; Exchange 2016 and 2013 need a legacy upgrade (new server), where the receive connector permission (Anonymous users) is set again and the connector is pointed at the new server. POPcon lists Exchange Server SE as compatible and delivers by SMTP only; MultiSendcon needs its send connector's source servers and smart host address checked.
- [Messages over 10 MB are not arriving: size limits between the POP3 connector and Exchange](https://www.servolutions.com/guides/exchange-message-size-limit-pop3-connector): Exchange limits message size for the organization (10 MB receive and send by default per Microsoft for 2016, 2019 and SE), on the receive connector (36 MB; 10 MB on Exchange 2007/2010 per the knowledge base) and on the mailbox, and enforces the most restrictive limit; a message refused at the receive connector waits in POPcon's TOOLARGE folder and is resent through PICKUP, one refused after acceptance produces a non-delivery report from Exchange.
- [Hosting several companies or domains on one Exchange Server](https://www.servolutions.com/guides/multiple-domains-one-exchange-server): one Exchange organization can hold several authoritative accepted domains with one email address policy per company; inbound each domain arrives by MX or is collected from provider mailboxes; outbound Exchange selects a send connector by recipient domain, never by sender, so a relay that routes by sender (MultiSendcon) uses one provider account and login per sender domain. Accepted domains, the default domain and the address book stay shared.
- [NDRs for external senders behind a POP3 connector](https://www.servolutions.com/guides/ndr-external-senders-pop3-connector): behind a POP3 connector the provider has already accepted the message, so the sender learns about an unknown recipient or an oversized message only if Exchange accepts it and generates the non-delivery report itself (POPcon does not generate NDRs); POPcon can instead re-route unknown recipients to the postmaster; reports and out-of-office replies leave with an empty envelope sender, which IONOS refuses since January 2024 unless a relay such as MultiSendcon fills in a sender address.
- [POP3/IMAP over TLS for mail retrieval: ports 995 and 993, STARTTLS vs implicit TLS, and "-ERR Command is not valid in this state"](https://www.servolutions.com/guides/pop3-imap-tls-ports-starttls): POP3 and IMAP encrypt either implicitly on a dedicated port (995 / 993, encrypted before the first command; Microsoft: "always SSL/TLS") or by STARTTLS / STLS on the plain port (110 / 143; Microsoft: "opportunistic TLS"); Exchange Online documents outlook.office365.com 995 and 993 with SSL/TLS and smtp.office365.com 587 with STARTTLS. Sending STLS on port 995 is refused with "-ERR Command is not valid in this state" because the session is already encrypted (Microsoft Q&A example). Connector settings (POPcon: server types POP3/POP3-SSL/IMAP/IMAP-SSL, encryption TLS/SSL/STLS/SPA, TLS 1.2 and 1.3), TLS-version timeouts of pre-4.0 versions, SMTP twins 504 5.7.4 and 530 5.7.0, symptom table.
- [Antispam and antivirus for POP3/IMAP-collected mail before it reaches Exchange: RBL checks, tagging, quarantine](https://www.servolutions.com/guides/antispam-antivirus-pop3-collected-mail): Connector-delivered mail bypasses the filters in front of the MX and reaches Exchange from the connector host, so Exchange connection filtering (Edge Transport only, judges the connecting IP) never sees the original sender; the connector checks the Received-header IPs against DNS blacklists, tags, diverts or deletes, applies white/blacklists and scans attachments before SMTP submission; slow checks and "everything is spam" are DNS problems.

## Support

- [Knowledge base](https://www.servolutions.com/support/knowledgebase): Exchange SMTP error codes, POP3/IMAP connector configuration, OAuth2 for Microsoft 365, migration and licensing articles.
- [Support](https://www.servolutions.com/support): Contact the support team by email or phone.
- [Exchange configuration guides](https://www.servolutions.com/support/config-exchange-2010): Configuring Exchange Server (2000–2013) to receive mail from POPcon.

## Company

- [About Servolutions](https://www.servolutions.com/about)
- [Contact](https://www.servolutions.com/contact)