Colas Nahaboo personal site, with discussions about programming code, web and computing topics, surfing and SUPing, and various musings. Zola 2026-08-02T00:00:00+00:00 https://colas.nahaboo.net/tags/fastmail/atom.xml 2026-08-02T00:00:00+00:00 2026-08-02T00:00:00+00:00 Unknown https://colas.nahaboo.net/code/gmail-to-fastmail-sync-yourlabels/ <p><img src='gmail-to-fastmail.svg' align=right width=300>I moved to Fastmail some time ago, but like many of us I kept one foot in Gmail: <a rel="noopener external" target="_blank" href="https://www.fastmail.help/hc/en-us/articles/1500000278022-Using-other-email-addresses-with-fetch">Fastmail's "fetch"</a> tool keeps duplicating my incoming Gmail into my Fastmail account — a backup, an escape plan, and a bridge for family members who are not quite ready to leave Gmail yet.</p> <p>But there was a hole: the <strong>labels</strong> I add on Gmail after the initial migration (manually, or with my rules) were never reproduced on Fastmail. So I wrote <strong><a rel="noopener external" target="_blank" href="https://github.com/ColasNahaboo/gmail-to-fastmail">gmail-to-fastmail</a></strong>, a single Go binary that incrementally syncs your Gmail labels to Fastmail.</p> <h2 id="how-it-works">How it works<a class="zola-anchor" href="#how-it-works" aria-label="Anchor link for: how-it-works">🔗</a></h2> <p>It reads your Gmail via IMAP (read-only, <code>X-GM-LABELS</code>), and applies the labels on Fastmail via JMAP (a more efficient variant of IMAP), in batches of 10 000. Progress is kept in a local SQLite database, so each run resumes where the last one stopped — once caught up, a run takes about 15 seconds. Perfect for cron.</p> <h2 id="what-it-does">What it does<a class="zola-anchor" href="#what-it-does" aria-label="Anchor link for: what-it-does">🔗</a></h2> <ul> <li><strong>Labels mapped</strong>: your Gmail labels become Fastmail labels, created on demand, never deleted.</li> <li><strong>Categories</strong>: Gmail's system categories (Inbox, Updates, Social...) become underscore-prefixed labels <code>_Inbox</code>, <code>_Updates</code>, <code>_Social</code>...</li> <li><strong>Trash</strong>: emails deleted on Gmail are not deleted on Fastmail, just labelled <code>_Trash</code> — a backup of your deleted mail, with an easy way to "empty the bin".</li> <li><strong>Local cache</strong>: unchanged emails are skipped, so Fastmail's API is left in peace.</li> <li><strong>Mirror mode</strong>: <code>-m</code>/<code>-M</code> optionally imports emails missing on Fastmail, not just labels. There are more options, detailed on the GitGub repository.</li> </ul> <h2 id="installation-usage-and-more-info">Installation, Usage, and more info<a class="zola-anchor" href="#installation-usage-and-more-info" aria-label="Anchor link for: installation-usage-and-more-info">🔗</a></h2> <p>See the <a rel="noopener external" target="_blank" href="https://github.com/ColasNahaboo/gmail-to-fastmail">GitHub repository</a>.</p> <h2 id="why-go">Why Go?<a class="zola-anchor" href="#why-go" aria-label="Anchor link for: why-go">🔗</a></h2> <p>Because it is a single self-contained binary with no runtime dependencies — you know my <a href="/blog/go-single-binary-fanatic">thing about that</a>. No Python env, no node_modules, no nothing. Free (MIT).</p> <p>Also, AI co-written: don't like, don't use.</p>