Phone email client is trying imap.fastmail.com/2607:7700:0:1e:0:1:426f:488 and timing out. Now that I think about it, this started when I left the house/wifi. Must be something weird about the mobile network connection. I just switched carriers.
Perhaps your mail client cached the ipv4 and ipv6 when you were at home and your client is preferring ipv6. Try looking up the method to flush DNS cache for your make/model of phone and see if that helps. Perhaps a power-cycle would suffice.
Try turning airplane mode on/off, and/or disable wifi. You wont be able to load the site by IP either way. Also completely exit/terminate the fastmail app before doing any of this.
~ $ nmap 66.111.4.148
Starting Nmap 7.92 ( https://nmap.org ) at 2022-11-05 17:12 EDT
Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn
Nmap done: 1 IP address (0 hosts up) scanned in 3.11 seconds
~ $ nmap 66.111.4.148
Starting Nmap 7.92 ( https://nmap.org ) at 2022-11-05 17:17 EDT
Nmap scan report for www.fastmail.com (66.111.4.148)
Host is up (0.029s latency).
Not shown: 997 filtered tcp ports (no-response)
PORT STATE SERVICE
53/tcp open domain
80/tcp open http
443/tcp open https
Nmap done: 1 IP address (1 host up) scanned in 4.96 seconds
7 comments
[ 3.1 ms ] story [ 37.6 ms ] threadWhat IP's do you get when you look up www.fastmail.com? Does it match the DNS propagation checker? [3]
Here is the TLS fingerprint I get from port 25:
[1] - https://www.ssllabs.com/ssltest/analyze.html?d=fastmail.com&...[2] - https://securityheaders.com/?q=https%3A%2F%2Fwww.fastmail.co...
[3] - https://www.whatsmydns.net/?#A/www.fastmail.com
~ $ nmap 66.111.4.148 Starting Nmap 7.92 ( https://nmap.org ) at 2022-11-05 17:17 EDT Nmap scan report for www.fastmail.com (66.111.4.148) Host is up (0.029s latency). Not shown: 997 filtered tcp ports (no-response) PORT STATE SERVICE 53/tcp open domain 80/tcp open http 443/tcp open https
Nmap done: 1 IP address (1 host up) scanned in 4.96 seconds
First time on mobile, second time on wifi.