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SPF TXT records larger than 255 characters
|SPF / TXT records larger than 255 characters
For some domains with complex email requirements, the SPF record can sometimes get too large to fit into a single record. There is typically a limit of 255 characters. As you can only have 1 SPF record per domain, what can you do? Well, mostly it is due to the inclusion of IP addresses. If you cannot consolidate multiple IP's into ranges, i.e. 192.168.0.1 192.168.0.4 192.168.0.65 to 192.168.0.0/24, then there is a trick you can use to split your SPF into multiple records and still meet the single record per domain requirement.
Start off by creating 2 or more (as needed ) SPF records for a sub domain. Call these sub1, sub2, etc. It would look like this
You can add as many subX records as you need to cater for all the hosts you need to add. These should be formatted as valid, complete, standalone SPF for thesub domains.
Now, for the main domain, you can 'include' these sub domains. Example below
A full example record might be 'v=spf1 include:sub1.mydomain.com include:sub2.mydomain.com -all'. This enables you to expand your SPF without many limits and should accommodate the most complex of requirements.
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