feat(rehan): update MX and TXT records for ImprovMX

Switching email providers to ImprovMX. This updates the MX and SPF records accordingly. The AAAA record remains the same.

Thank you!

domains/rehan.json

@@ -8,13 +8,11 @@
       "2a0b:4e07:8:1::869"
     ],
     "MX": [
-      { "priority": 10, "target": "mx.zoho.com" },
-      { "priority": 20, "target": "mx2.zoho.com" },
-      { "priority": 50, "target": "mx3.zoho.com" }
+      { "priority": 10, "target": "mx1.improvmx.com" },
+      { "priority": 20, "target": "mx2.improvmx.com" }
     ],
     "TXT": [
-      "v=spf1 include:zoho.com ~all",
-      "zoho-verification=zb38023323.zmverify.zoho.com"
+      "v=spf1 include:spf.improvmx.com ~all"
     ]
   },
   "proxied": true