Synchronize IMAP state without treating sequence numbers as stable IDs

Treat this document as a focused evidence review: Synchronize IMAP state without treating sequence numbers as stable IDs. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official RFC 9051 — Internet Message Access Protocol (IMAP) – Version 4rev2 from RFC Editor / Internet Engineering Task Force supports the following bounded statements:

• An IMAP UID remains stable during a session and normally across sessions; UIDVALIDITY tells a client when earlier UIDs can no longer be reused for synchronization. The research record locates this support at Section 2.3.1.1 (Unique Identifier Message Attribute).
• A message sequence number is only the message’s current relative mailbox position and can be reassigned when another message is expunged. The research record locates this support at Section 2.3.1.2 (Message Sequence Number Message Attribute).
• Each EXPUNGE immediately decrements the sequence numbers of following messages, so clients must apply untagged mailbox updates before interpreting later sequence-number responses. The research record locates this support at Section 7.5.1 (EXPUNGE Response).

These statements are the factual basis for this document. Do not extend them into a broader assurance. Review sending domains, receiving domains, message agents, headers, authentication results, policy records, and failure handling only where the source and recorded environment align.

What the source does not establish

This RFC evidence supports only the named mail-protocol decision; it does not prove provider support, deliverability, or compliance for a particular flow. Do not read the source as proof of implementation or permission to change production. Its guidance remains conditional on authoritative DNS, certificates, time, gateways, identity stores, reputation services, and third-party mail providers and the environment’s recorded constraints.

Applicability questions

• For source statement 1 at Section 2.3.1.1 (Unique Identifier Message Attribute), which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Section 2.3.1.2 (Message Sequence Number Message Attribute), which observable configuration, record, or test can confirm applicability here?
• For source statement 3 at Section 7.5.1 (EXPUNGE Response), which observable configuration, record, or test can confirm applicability here?
• Within sending domains, receiving domains, message agents, headers, authentication results, policy records, and failure handling, which versions, roles, and configuration states define the review population?
• Could authoritative DNS, certificates, time, gateways, identity stores, reputation services, and third-party mail providers invalidate the test, hide a failure, or change applicability?
• Who owns the decision, and which observation requires stopping, escalation, or rollback?

DSE recommendation:

DSE recommends using the cited source as the evidence anchor for this decision. Start with applicability, then compare the observed state with the cited source. Record the source location, examined part of sending domains, receiving domains, message agents, headers, authentication results, policy records, and failure handling, observed and expected states, owner, and reason for deviation.

Do not move from citation to production in one step. Pilot the decision where practical, observe agreed signals, retain a reversal point, and verify authoritative DNS, certificates, time, gateways, identity stores, reputation services, and third-party mail providers. Handle credentials, keys, recovery data, and personal information through approved secure channels.

Verification and evidence

Evidence should let another reviewer reproduce this decision. Retain observations beside the traced locations Section 2.3.1.1 (Unique Identifier Message Attribute); Section 2.3.1.2 (Message Sequence Number Message Attribute); Section 7.5.1 (EXPUNGE Response). Favor sanitized messages, DNS records, SMTP transcripts, authentication results, policy evaluation, and delivery or rejection logs, linked to stable identifiers, time, and operator.

Record the decision even when no change is made, including uncertainty and the next trigger. Use safe testing conditions for disruptive work, preserve rollback proof, and revisit the conclusion after relevant platform, dependency, vendor, or ownership changes.

Official references

• RFC 9051 — Internet Message Access Protocol (IMAP) – Version 4rev2 — RFC Editor / Internet Engineering Task Force