Is there an anonymous e-mail application that I can use to communicate with people in the Tor browser or would it be a problem if I communicate using Gmail?
I will just copy and paste from /u/HeadJanitor
Secure & Disposable Email Hosts
https://tuta.com
https://mailfence.com
https://www.guerrillamail.com
https://yopmail.com/en/email-generator (Generate Randomly an Anonymous Email for Free)
https://nbox.notif.me (Free Anonymous and Private Disposable Address Provider)
https://addy.io (Open-source Anonymous Email Forwarding)
https://www.secure-email.org
https://maildrop.cc
https://www.mailinator.com
https://www.secure-email.org
https://librem.one
https://flashbox.5july.org (Flashbox - Anonymous Disposable Email)
https://user.disroot.org/pwm/public/newuser (Disroot)
https://www.throwawaymail.com
https://nbox.notif.me (Anonymous, Private, Free)
http://csmail3thcskmzvjicww3qdkvrhb6pb5s7zjqtb3gdst6guby2stsiqd.onion (cs.email - Disposable Temporary E-Mail Address)
http://torbox36ijlcevujx7mjb4oiusvwgvmue7jfn2cvutwa6kl6to3uyqad.onion (TorBox)
http://6n5nbusxgyw46juqo3nt5v4zuivdbc7mzm74wlhg7arggetaui4yp4id.onion/src/register.php (Morke)
http://mail2torjgmxgexntbrmhvgluavhj7ouul5yar6ylbvjkxwqf6ixkwyd.onion (Mail2Tor)
http://2nxpboa3ya52j5au4gxwkdt4nxoh5g4y4f3tuqedlza46y35jmv6doid.onion (SecretMail)
http://ovhcd6qhuz22bid42pw7unwfqf7i55rghb5x62q4kxchjnk2gz2ot6id.onion (Hobe Onion Mail)
http://5nm4mdhzyfbif6i5qv3kh4i7j2trlbuvujsencsqn55opaa3d6qhfcqd.onion (Hidden Mail Onion Server)
https://onionmail.org (Clearnet)
http://pflujznptk5lmuf6xwadfqy6nffykdvahfbljh7liljailjbxrgvhfid.onion (Onion Mail)
http://en.vzoc4aylgsqwexe6okjbz2ix5atgdv5xyibnkcekmtg4u23syz6a7rid.onion (OnionMail)
http://j3bv7g27oramhbxxuv6gl3dcyfmf44qnvju3offdyrap7hurfprq74qd.onion (adunanza Onion Mail)
http://eot3almpracnkz7gz3r5yr3qaymngqsrmvbica2shw5zuc52az2gxoqd.onion (Dozaru Onion Mail)
http://2nxpboa3ya52j5au4gxwkdt4nxoh5g4y4f3tuqedlza46y35jmv6doid.onion (Systemli)
https://www.systemli.org/en/ (Systemli Clearnet)
http://fozdean5ayswi6jtseg2fgyysqt3dskoosmoc6gnqia4dxwxiuvg3oad.onion | Underworld.dog Onion Email
But also check out /d/OpSec/wiki/?id=bc728252
Secure & Disposable Email Hosts
https://tuta.com
https://mailfence.com
https://www.guerrillamail.com
https://yopmail.com/en/email-generator (Generate Randomly an Anonymous Email for Free)
https://nbox.notif.me (Free Anonymous and Private Disposable Address Provider)
https://addy.io (Open-source Anonymous Email Forwarding)
https://www.secure-email.org
https://maildrop.cc
https://www.mailinator.com
https://www.secure-email.org
https://librem.one
https://flashbox.5july.org (Flashbox - Anonymous Disposable Email)
https://user.disroot.org/pwm/public/newuser (Disroot)
https://www.throwawaymail.com
https://nbox.notif.me (Anonymous, Private, Free)
http://csmail3thcskmzvjicww3qdkvrhb6pb5s7zjqtb3gdst6guby2stsiqd.onion (cs.email - Disposable Temporary E-Mail Address)
http://torbox36ijlcevujx7mjb4oiusvwgvmue7jfn2cvutwa6kl6to3uyqad.onion (TorBox)
http://6n5nbusxgyw46juqo3nt5v4zuivdbc7mzm74wlhg7arggetaui4yp4id.onion/src/register.php (Morke)
http://mail2torjgmxgexntbrmhvgluavhj7ouul5yar6ylbvjkxwqf6ixkwyd.onion (Mail2Tor)
http://2nxpboa3ya52j5au4gxwkdt4nxoh5g4y4f3tuqedlza46y35jmv6doid.onion (SecretMail)
http://ovhcd6qhuz22bid42pw7unwfqf7i55rghb5x62q4kxchjnk2gz2ot6id.onion (Hobe Onion Mail)
http://5nm4mdhzyfbif6i5qv3kh4i7j2trlbuvujsencsqn55opaa3d6qhfcqd.onion (Hidden Mail Onion Server)
https://onionmail.org (Clearnet)
http://pflujznptk5lmuf6xwadfqy6nffykdvahfbljh7liljailjbxrgvhfid.onion (Onion Mail)
http://en.vzoc4aylgsqwexe6okjbz2ix5atgdv5xyibnkcekmtg4u23syz6a7rid.onion (OnionMail)
http://j3bv7g27oramhbxxuv6gl3dcyfmf44qnvju3offdyrap7hurfprq74qd.onion (adunanza Onion Mail)
http://eot3almpracnkz7gz3r5yr3qaymngqsrmvbica2shw5zuc52az2gxoqd.onion (Dozaru Onion Mail)
http://2nxpboa3ya52j5au4gxwkdt4nxoh5g4y4f3tuqedlza46y35jmv6doid.onion (Systemli)
https://www.systemli.org/en/ (Systemli Clearnet)
http://fozdean5ayswi6jtseg2fgyysqt3dskoosmoc6gnqia4dxwxiuvg3oad.onion | Underworld.dog Onion Email
But also check out /d/OpSec/wiki/?id=bc728252