Emails containing shortlinks from „bit.ly“ and „tinyurl.com“ etc. are banned by many email providers.
These URL Shortener services are being misused to distribute spam, malware, virus and phishing attacks via their short links.
Therefore emails which contain such short links will probably end up in the spam (abuse) folder or may no longer be delivered or forwarded.
Top 10 of abused redirectors (URL Shorteners):
bit.ly
6url.ru
tinyurl.com
ow.ly
tiny.cc
goo.gl
migre.me
t.co
bit.do
x.co
Details:
http://www.surbl.org/tld
The solution to this problem is to use the real URL (links) or shorten your URLs using your custom domain name.
example from gmail:
(host alt1.gmail-smtp-in.l.google.com[142.250.150.27] said: 421-4.7.0 [15] Our system has detected that this message is 421-4.7.0 suspicious due to the nature of the content and/or the links within. 421-4.7.0 To best protect our users from spam, the message has been blocked. 421-4.7.0 Please visit 421 4.7.0 https://support.google.com/mail/answer/188131 for more information.