sending text to my cell phone using @tmomail.net no longer working?

Actually I made a mistake with my dig command. I forgot to ask for the MX (mail exchange) record which is the email address of T-Mobile's systems:

dig -t mx tmomail.net @8.8.8.8

; <<>> DiG 9.18.12-0ubuntu0.22.04.2-Ubuntu <<>> -t mx tmomail.net @8.8.8.8
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27536
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;tmomail.net.                   IN      MX

;; ANSWER SECTION:
tmomail.net.            309     IN      MX      10 tmo-east.mx.a.cloudfilter.net.
tmomail.net.            309     IN      MX      10 tmo-west.mx.a.cloudfilter.net.

;; Query time: 44 msec
;; SERVER: 8.8.8.8#53(8.8.8.8) (UDP)
;; WHEN: Sat Jul 08 08:17:09 EDT 2023
;; MSG SIZE  rcvd: 107

I own a Wireless Internet Service Provider (WISP) and using our commercial email servers I am able to send text message to myself.

From my own commercial email server

Jul  8 08:15:20 smtp2 postfix/smtp[857458]: BD36A8003A: to=<603xxxxxxx@tmomail.net>, relay=tmo-east.mx.a.cloudfilter.net[34.232.155.8]:25, delay=1.2, delays=0.03/0.01/0.38
/0.8, dsn=2.0.0, status=sent (250 2.0.0 I6qNqMmCvdLyJI6qOqEW9U mail accepted for delivery)

The above indicates T-Mobile sms/email server accepted the message and with a few seconds I got the text message on my phone, but from my outlook email I got back the following response:

Delivery has failed to these recipients or groups:

603xxxxxxx@tmomail.net (603xxxxxxx@tmomail.net)
Your message couldn't be delivered. Despite repeated attempts to contact the recipient's email system it didn't respond.

Contact the recipient by some other means (by phone, for example) and ask them to tell their email admin that it appears that their email system isn't accepting connection requests from your email system. Give them the error details shown below. It's likely that the recipient's email admin is the only one who can fix this problem.

For more information and tips to fix this issue see this article: https://go.microsoft.com/fwlink/?LinkId=389361.

Similar response from my gmail account it...almost seems like an aggressive email filter is in place with T-mobile.

You might want to update your ticket with this info.