DNS Zone TXT Records limited to 255 characters - need more

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Good day,

New to Amazon Lightsail here. Migrating my instance off another vendor. Instance, firewall, static ip - all went ok. Now setting up my DNS Zone. One of my DNS TXT records is about 400 characters long. It is a google-generated DKIM record which contains key-value pairs including a public key.

When I try to add the record in the DNS Zone Editor, an error pops up: "Each line must be between 0 and 255 characters and contain only printable ASCII characters". But since the 400 characters contain a public key, I don't think I should break it up. Is there any solution to this?

Thanks -Ricardo

Edited by: RigaDorje on Jun 17, 2019 7:42 PM

Edited by: RigaDorje on Jun 17, 2019 7:43 PM

asked 5 years ago1011 views
2 Answers
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Accepted Answer

Strings in SPF and TXT records should be no longer than 255 characters. However to get around this limitation, per RFC 4408 a TXT or SPF record is allowed to contain multiple strings, which should be concatenated together by the reading application.
-- https://kb.isc.org/docs/aa-00356

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David G
answered 5 years ago
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Hi David G,

Thanks for the information and the reference link. I broke up the long string by making several lines each less than 255 chars (separated using the Enter key) -- trusting that the reading application will reassemble it back correctly. The editor saved my record.

I then used Mxtoolbox's DKIM Lookup tool https://mxtoolbox.com/dkim.aspx to query the DNS record. It interpreted the DKIM record correctly.

Thank you! -Ricardo

answered 5 years ago

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