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Searching
Searching happens on the IMAP server, not in the browser. Tachyon keeps no local index of your mail, so what you can search for is what your server can answer, and how fast it answers depends on the server rather than on Tachyon.
Type words and they are searched as text. What "as text" means is set by the administrator: with message_list_fast_simple_search on, which is the default, a plain search looks at From, To, Cc and Subject only. Turn it off and the whole message body is searched too, which is thorough and much slower on a large mailbox. See the admin manual.
The arrow at the right of the search box opens a form for the common criteria: sender, recipient, subject, body text, a tag, attachments, unread, starred, replied, how far back to look, and whether to include subfolders.
Whatever you pick there ends up in the search box as text, which is worth knowing: the form writes the same syntax you can type yourself, and it understands more keys than the form offers.
Criteria are key=value, joined with &:
from=alice&subject=invoice&unseen
since=2026-01-01&before=2026-03-01
| Key | Matches |
|---|---|
from= |
From |
to= |
To, and also Cc and Bcc unless you add &to-only
|
mail= |
From or To or Cc |
subject= |
Subject |
text= |
the whole message, body included |
header= |
any header, name and value separated by a space: header=X-Mailer Thunderbird
|
keyword= |
a tag, as the server names it |
since= |
received on or after a date, YYYY-MM-DD
|
before= |
received strictly before a date |
on= |
received on one date |
sentsince=, sentbefore=, senton=
|
the same three against the Date header rather than when the server took delivery |
size=, minsize=, bigger=
|
larger than, suffix K or M
|
maxsize= |
smaller than |
in= |
subtree for this folder and everything under it, subtree-one for one level down |
These take no value, so write them on their own: attachment, unseen, seen, flagged, unflagged, answered, unanswered, deleted, undeleted, to-only.
A date range is since= and before= together. since= includes its date and before= excludes its own, so since=2026-01-01&before=2026-03-01 is the whole of January and February.
in=subtree needs the server to support MULTISEARCH. Where it does not, the administrator can enable search_subtree_fallback, which searches each folder of the subtree in turn instead. That costs one IMAP search per folder, so it is noticeably slower on a deep hierarchy. Servers that do support MULTISEARCH always use it and ignore the fallback.
Dates are whole days. IMAP date searches disregard time and timezone by specification, so there is no way to ask for "after 14:00 on Tuesday". Mail clients that offer this keep a local copy of your mail to search; Tachyon deliberately does not.
Sorting and threading are the server's too. If sorting seems to ignore a criterion, check which extensions your server offers under IMAP capabilities.
An older key:value form is also accepted, and is used when the search begins with a recognised key followed by a colon. It is kept for compatibility and the two forms do not accept quite the same keys, so prefer key=value.