If it is a case you need to enter multiple entries for an SPF TXT record, for a domain, it is suggested that you split the record up into multiple smaller records.
Consider the following SPF record for ‘sampledomain.com’ – note that the entries are for example purposes only.
sampledomain.com TXT
v=spf1 a mx a:mail.domain.com a:mail.domain.ie a:server5.somedomain.com a:server7.somedomain.com mx:server95.somedomain.com include:thatdomain.com ip4:192.168.0.1 ip4:192.168.0.2 ip4:192.168.03 ip4:192.168.0.4 ip4:192.168.0.04 -all
This record above is too long and needs to be shortened; you will have to split this up into two or more records and include them in the main SPF record.
Create the following SPF records on the domain name:
- spf1.sampledomain.com TXT
v=spf1 a mx a:mail.domain.com a:mail.domain.ie a:server5.somedomain.com -all - spf2.sampledomain.com TXT
v=spf1 server7.somedomain.com mx:server95.somedomain.com include:thatdomain.com -all - spf3.sampledomain.com TXT
v=spf1 ip4:192.168.0.1 ip4:192.168.0.2 ip4:192.168.03 ip4:192.168.0.4 ip4:192.168.0.04 -all
Note: You can create more records as required.
Then amend the initial SPF as follows:
sampledomain.com TXT
v=spf1 include:spf1.sampledomain.com include:spf2.sampledomain.com include:spf3.sampledomain.com -all”
Once DNS updates, all records would be read as one by recipient servers.
Source : https://help.blacknight.com/hc/en-us/articles/212512389-Creating-large-SPF-records-with-many-entries