jstedfast/MailKit · error · NotSupportedException

The SAVEDSINCE search term is not supported by the IMAP…

Error message

The SAVEDSINCE search term is not supported by the IMAP server.

What it means

BuildQuery throws this NotSupportedException when a SearchQuery.SavedSince(date) term is used but the server does not advertise the SAVEDATE capability (RFC 8514). SAVEDSINCE matches messages whose savedate is on or after the given date. The capability gate fires during client-side query compilation in BuildQuery.

Solutions

Check (client.Capabilities & ImapCapabilities.SaveDate) != 0 before using SavedSince.
Fall back to SearchQuery.DeliveredSince(date) or use UIDVALIDITY/condestore-style sync mechanisms instead.
Upgrade to an SAVEDATE-capable server if savedate-driven incremental sync is a requirement.

Example fix

// before
var uids = folder.Search(SearchQuery.SavedSince(lastSync));

// after
var uids = (client.Capabilities & ImapCapabilities.SaveDate) != 0
    ? folder.Search(SearchQuery.SavedSince(lastSync))
    : folder.Search(SearchQuery.DeliveredSince(lastSync));

Defensive patterns

Strategy: fallback

Validate before calling

var q = (client.Capabilities & ImapCapabilities.SaveDate) != 0
    ? SearchQuery.SavedSince(date)
    : SearchQuery.DeliveredSince(date);

Type guard

bool SupportsSaveDate(ImapClient c) => (c.Capabilities & ImapCapabilities.SaveDate) != 0;

Try / catch

try {
    return folder.Search(SearchQuery.SavedSince(lastSync));
} catch (NotSupportedException) {
    return folder.Search(SearchQuery.DeliveredSince(lastSync));
}

Prevention

For incremental sync prefer UID-based tracking over any date-based term.
Check ImapCapabilities.SaveDate before any Saved* search term.
Unit-test search building against a capability set that mimics your production server.

When it happens

Trigger: Calling folder.Search(SearchQuery.SavedSince(someDate)) or combining it in an AND/OR expression on a server without ImapCapabilities.SaveDate.

Common situations: Incremental-sync code using savedate as a change cursor run against servers without SAVEDATE; Gmail/Exchange migrations are typical.

Related errors

AI-assisted analysis of jstedfast/MailKit@9d3859a785 (2026-09-15). Data as JSON: /api/errors/797060c0ea89b2f4. Report an issue: GitHub.

Appendix: source

Thrown at MailKit/Net/Imap/ImapFolderSearch.cs:313

			case SearchTerm.SavedBefore:
				if ((Engine.Capabilities & ImapCapabilities.SaveDate) == 0)
					throw new NotSupportedException ("The SAVEDBEFORE search term is not supported by the IMAP server.");

				date = (DateSearchQuery) query;
				builder.Append ("SAVEDBEFORE ");
				builder.Append (FormatDateTime (date.Date));
				break;
			case SearchTerm.SavedOn:
				if ((Engine.Capabilities & ImapCapabilities.SaveDate) == 0)
					throw new NotSupportedException ("The SAVEDON search term is not supported by the IMAP server.");

				date = (DateSearchQuery) query;
				builder.Append ("SAVEDON ");
				builder.Append (FormatDateTime (date.Date));
				break;
			case SearchTerm.SavedSince:
				if ((Engine.Capabilities & ImapCapabilities.SaveDate) == 0)
					throw new NotSupportedException ("The SAVEDSINCE search term is not supported by the IMAP server.");

				date = (DateSearchQuery) query;
				builder.Append ("SAVEDSINCE ");
				builder.Append (FormatDateTime (date.Date));
				break;
			case SearchTerm.Seen:
				builder.Append ("SEEN");
				break;
			case SearchTerm.SentBefore:
				date = (DateSearchQuery) query;
				builder.Append ("SENTBEFORE ");
				builder.Append (FormatDateTime (date.Date));
				break;
			case SearchTerm.SentOn:
				date = (DateSearchQuery) query;
				builder.Append ("SENTON ");
				builder.Append (FormatDateTime (date.Date));
				break;

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