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Troubleshoot UIDVALIDITY errors

When syncing email messages with a provider, Nylas requires a persistent unique identifier across sessions to ensure data remains consistent and up-to-date. When Nylas syncs an IMAP account, it uses two important identifiers to link the locally cached email messages with those that exist on the IMAP server:

If any UIDs changed between sessions, the provider uses the UIDVALIDITY value to signal that you need to clear your cache and look for the new UIDs assigned to email messages.

⚠️ For misconfigured providers, the UIDVALIDITY value might change with every session. Nylas uses several concurrent sessions to monitor IMAP accounts, and if each one has a different set of UIDs, maintaining data consistency is impossible. In these cases, Nylas stops syncing and presents a "Stopped due to too many UIDVALIDITY resyncs" error.

Error: Stopped due to too many UIDVALIDITY resyncs

Resynced more than MAX_UIDINVALID_RESYNCS in a row. Stopping sync.

If an account is in a Stopped state and the mailsync logs return the error above, this indicates that Nylas stopped syncing the account due to inconsistent UIDVALIDITY values between sessions. Because Nylas syncs across multiple sessions for an account, if UIDVALIDITY changes constantly, Nylas cannot link IMAP UIDs and cannot maintain consistent user data.

⛔️ Servers with inconsistent UIDVALIDITY are not supported until they adhere to the standards set forth in the RFC standard document. Nylas cannot work around the issue.

UIDVALIDITY and empty folders

In some cases, the UIDVALIDITY error is triggered on folders which contain no email messages (and so have no UIDVALIDITY values). If this happens, the end user can either delete their empty folders as a workaround, or they can put at least one email message in every empty folder to generate its UIDVALIDITY value and allow their account to resync.

UIDVALIDITY and Amazon WorkMail

Resynced more than MAX_UIDINVALID_RESYNCS in a row. Stopping sync.

If you connected an Amazon WorkMail account to Nylas using IMAP, you might see your account in a Stopped state and see an error in the mailsync logs like the error above. The error message indicates that the email server does not maintain consistent UIDVALIDITY values, which is incompatible with Nylas.

You might be able to solve this issue by authenticating your Amazon WorkMail account using Microsoft Exchange's advanced login settings and specifying one of the following server addresses, depending on your account region:


Unsupported providers

Due to latency and errors with UID, the Vodaphone IMAP provider is not supported.