Often the most famous generic URL shorteners get blacklisted. If you send an email containing links shortened with generic, common domains that are blacklisted, your email will probably end up in the spam (abuse) folder of your audience.
Why does this happen, though? Generic domains are used by millions of people, including spammers to share malware, phishing content and any sort of illegal stuff. Anyone can create an account and create his short link for free and it’s really difficult to check every single link that has been created.
SURBL maintains an updated list of the top 10 most abused URL shorteners (Blacklisted).
Following the list updated Aug, 22, 2020:
1. bit.ly 2. bit.do 3. ow.ly 4. goo.gl 5. x.co 6. rebrand.ly 7. tinyurl.com 8. t.co 9. is.gd 10. ht.ly
The solution to this problem is to shorten your URLs using your custom domain name as a redirector. In this way, only you are able to create links with that domain and, unless you are a spammer, you won’t be blacklisted.
Also you may want to take a loot at the most abusive TLD’s to avoid using them for redirects and/or your primary wesbite (.com here is just before it have the most registrations – so it’s not the rule):
Below are the top 20 TLDs listed in SURBL (unique counts). Numbers on the left are counts of the domains in the TLDs on the right: 185591 com 46330 work 37474 xyz 25346 top 21889 site 20419 net 19167 live 18833 cn 15347 icu 15250 wang 10072 fit 9502 vip 9258 ru 8628 life 6342 cam 6117 us 5649 rest 4442 biz 4370 co 4192 agency