[dbezverkhnii]

Yahoo and AOL cap the simultaneous sessions per mailbox (5 and 8, measured) and refuse one more login with an untagged * BYE followed by the tagged refusal — N NO [LIMIT] AUTHENTICATE Rate limit hit. for XOAUTH2, N NO [LIMIT] LOGIN Rate limit hit. for a password. libetpan stops at the BYE with MAILIMAP_ERROR_STREAM, so the login reported ErrorConnection, and the client retried at once — one more login against the same limit.

• The tagged refusal is still in imap_stream_buffer after the BYE. On a stream error the login looks there for NO [LIMIT] (the RFC 5530 code, not the text after it, which echoes the login command) and reports the new ErrorIMAPTooManySimultaneousConnections, the counterpart of Gmail's ErrorGmailTooManySimultaneousConnections. Spark handles both the same way: it narrows the account's connections for a while instead of retrying.
• The code is appended after ErrorCanceled in the C++, C and Swift enums, so no existing value moves. Like ErrorCanceled, it has no ObjC constant and no localized description.
• Nothing else in the login changes: a bare BYE stays ErrorConnection, Gmail's texts and wrong credentials keep their codes.

The C++ changed, so the Windows prebuilt needs a rebuild for this revision before a tag.

Tests: IMAPLoginTests against LeaseTestTCPEndpoint, which can now answer a command with a refusal and close the socket. * BYE + NO [LIMIT] gives the new code (it gave ErrorConnection before the fix); a bare BYE, Gmail's text and [AUTHENTICATIONFAILED] keep theirs. Checked in Spark against Yahoo and AOL with two devices on one account.

🤖 Generated with Claude Code

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Note

Medium Risk
Touches IMAP login error classification on stream failures; mis-detection could change client retry/backoff behavior, though scope is narrow (substring on buffered stream after BYE).

Overview
Adds ErrorIMAPTooManySimultaneousConnections (C/C++/Swift) so Yahoo/AOL session-cap refusals are not reported as generic connection failures.

When libetpan returns MAILIMAP_ERROR_STREAM after an untagged * BYE, IMAPSession::login inspects imap_stream_buffer for the tagged NO [LIMIT] (RFC 5530) and returns the new code—parallel to Gmail’s ErrorGmailTooManySimultaneousConnections. A bare BYE, Gmail “too many connections” text, and AUTHENTICATIONFAILED behavior is unchanged.

LeaseTestTCPEndpoint gains configurable refusals (custom reply + optional socket close). IMAPLoginTests cover * BYE + [LIMIT], Gmail text, auth failure, and BYE-only cases for LOGIN and XOAUTH2.

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