jstedfast/MailKit · error · NotSupportedException

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

Error message

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

What it means

BuildQuery throws this NotSupportedException when a SearchQuery.SavedOn(date) term is used but the server lacks the SAVEDATE capability (RFC 8514). SAVEDON matches messages whose savedate falls on the given date. MailKit validates ImapCapabilities.SaveDate while serializing the query and throws before issuing the command.

Solutions

Check (client.Capabilities & ImapCapabilities.SaveDate) != 0 before using SavedOn.
Use SearchQuery.DeliveredOn(date) (INTERNALDATE) as a universal fallback.
Move to a server implementing RFC 8514 if save-date accuracy is required.

Example fix

// before
var uids = folder.Search(SearchQuery.SavedOn(DateTime.Today));

// after
var day = DateTime.Today;
var uids = (client.Capabilities & ImapCapabilities.SaveDate) != 0
    ? folder.Search(SearchQuery.SavedOn(day))
    : folder.Search(SearchQuery.DeliveredOn(day));

Defensive patterns

Strategy: fallback

Validate before calling

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

Type guard

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

Try / catch

try {
    return folder.Search(SearchQuery.SavedOn(date));
} catch (NotSupportedException) {
    return folder.Search(SearchQuery.DeliveredOn(date));
}

Prevention

Group all SAVEDATE search terms behind a single SupportsSaveDate guard.
Verify SAVEDATE support against each deployment target before shipping.
Keep a portable RFC 3501-only search builder for cross-provider code.

When it happens

Trigger: Calling folder.Search(SearchQuery.SavedOn(someDate)) on a server whose capabilities exclude ImapCapabilities.SaveDate.

Common situations: Same family as SavedBefore/SavedSince: code written against SAVEDATE-capable servers (newer Dovecot/Cyrus) deployed to Gmail, Exchange, or older servers.

Related errors

AI-assisted analysis of jstedfast/MailKit@9d3859a785 (2026-09-15). Data as JSON: /api/errors/c84bf6cd099ce37a. Report an issue: GitHub.

Appendix: source

Thrown at MailKit/Net/Imap/ImapFolderSearch.cs:305

				builder.Append ("RECENT");
				break;
			case SearchTerm.SaveDateSupported:
				if ((Engine.Capabilities & ImapCapabilities.SaveDate) == 0)
					throw new NotSupportedException ("The SAVEDATESUPPORTED search term is not supported by the IMAP server.");

				builder.Append ("SAVEDATESUPPORTED");
				break;
			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;

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