What are typical key length recommendations?
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DKIM uses public-key cryptography to sign your outgoing email. The key length determines how hard it is to crack that signature. Longer keys are stronger but also create larger DNS TXT records, which can cause their own headaches.
The standard: 2048-bit
2048-bit is what most senders should use today. It's supported by all major ESPs and DNS providers, it meets the IETF and NIST recommendations, and it's what Gmail, Outlook, and Yahoo expect when evaluating your authentication. If you set up DKIM in the last few years and accepted your ESP's default, you're almost certainly on 2048 already.
1024-bit: avoid it if you can
1024-bit RSA keys are considered weak by modern cryptographic standards. NIST deprecated them for most uses years ago. Some older ESPs still default to 1024, and some DNS providers couldn't support longer TXT records. Most can now. If you're stuck on 1024 for a legacy reason, check whether your DNS provider supports longer TXT values before assuming you can't upgrade. If you can migrate, do it.
4096-bit: overkill with real tradeoffs
4096-bit keys offer stronger protection, but the resulting TXT record often exceeds 512 bytes (the safe size for a single DNS UDP packet). Some DNS implementations split the record across multiple strings and some mail servers parse that poorly. It's technically valid but creates unnecessary compatibility risk. 2048 is the sweet spot between security and compatibility.
You can check your current key length and DNS propagation with our DKIM checker. If you're migrating from 1024 to 2048 and want to walk through it safely without breaking delivery, the SOS hotline is free.
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