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hMailServer Community Forum
hMailServer 6.3.3 — signed 15 September 2026, Windows and Linux, database schema 6040, and a drop-in upgrade from any 5.x install.Download 6.3.3 Documentation
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  3. hMailServer 6.3.3: outbound BDAT stalled every message over 60,000 bytes

hMailServer 6.3.3: outbound BDAT stalled every message over 60,000 bytes

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releasebugfixsmtpsecurityschema
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    Progressiverobot
    hMailServer Team
    wrote last edited by
    #1

    Every message over 60,000 bytes sent to a server advertising CHUNKING has stalled since outbound BDAT arrived in 6.2.25. Every release from 6.2.25 to 6.3.2 is affected. If your smart host or the destination offers CHUNKING, large mail has been failing, and OutboundChunking=0 is the workaround on any of them. 6.3.3 fixes it (issue #261).

    The SMTP client armed the read for the reply as soon as the BDAT command, or with PIPELINING the envelope, had been queued, and the chunk's second 60,000-byte buffer was queued behind that read in the operation queue, which starts only the operation at its head. The read could not complete while the remote waited for the bytes behind it, so nothing sent them, and the remote gave up on its own timeout. iCloud returned 421 after five minutes in the report. DATA never met it, because its body streams only after the 354. The queue now runs once more after a read has started. If you cannot upgrade yet, OutboundChunking=0 in hMailServer.ini is the workaround.

    Before you upgrade

    Two schema changes, both upgrade in place. Schema 6039 widens a domain's relay-password column: it held 255 characters and a DPAPI envelope is 314, so a relay password could not be saved on any Windows installation. Schema 6040 adds the CardDAV tables.

    On PostgreSQL the escaper doubled backslashes unconditionally, which is correct only while standard_conforming_strings is off, and that has been on by default since PostgreSQL 9.1. DKIM key-file paths, signatures, vacation messages and rules were stored doubled. Values already stored that way stay as they are. Edit and save them once.

    Also in this release

    • The four [Settings] ini routes over REST answered to any api key. A read-only key could read the OAuth2 HMAC secret, the password pepper and the service account password, and a write key could set AutoBanCommand, which the firewall reconciliation runs as the service. They take the administrator password only now. A domain-scoped key is refused the eleven administrator-only fields on PUT /api/v1/domains/{domain} with 403.
    • CardDAV (RFC 6352) for the account's address book, one book named Contacts, vCard 3.0 and 4.0, HTTP Basic over HTTPS only. The web services HTTPS listener has to be on (WebServicesHttpsPort).
    • The webmail is rebuilt: inbox tabs, mute, pinning as $Pinned, follow-up dates as $FollowUp and $Due-YYYY-MM-DD, fourteen more search operators, twenty languages.
    • The full-text indexer no longer reports an error for a message deleted before its terms were saved.

    Full release notes, checksums and signatures

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