How can I encrypt attachments send by Filelink like normal attachments?

Question

In the help of the Filelink functionallity I could not find any instruction how to encrypt attachments send by Filelink in the same way as by the normal e-mail attachment (SSL).
Is there no possibility to do this or is it just not described. If it is, please send me a link.
Thanks.

Answer 1

Hello Guys,
thanks for some further insight. @Zenos pointed out, that some e-mail providers only encrypt the Login data by SSL/TLS and not the message and attachment. Therefore I checked this on the website of my provider GMX and luckily they encrypt the Login, message and attachement of every e-mail. As far as the recipient also uses such a provider, then all the data are encrypted on the ways between me and my provider, my provider and his provider, his provider and him. Since this year, all the big providers in Germany introduced this full SSL encryption for all data send by e-mail (http://www.e-mail-made-in-germany.de/Verschluesselung.html).
I understand that additional encryption by programmes like S/MIME or GPG does this too but has the additional advantage that the data are encrypted while being on the servers. The bad side of this methods seems to be some additional effort to exchange keys between recipient and sender - although it is not clear to me whether this is done over the internet or phoning or paper mail is necessary.
Thanks to @christ1 for pointing out that Filelink uses HTTPS, which means that it has the same security level as my normal e-mails with standard attachment, since they are send by SSL/TLS, but not encrypted on the servers. This seems to be identical when using Filelink. This answers my question. Thanks to both. :-)
Actually I found that the problem, why I didn't get this from the mozilla help page is that I read the German mozilla help page which has a translation error. The English help page is clearly saying "Note that standard attachment functionality is also not encrypted." (Which can be easily overcome, if you switch SSL/TLS on in Thunderbird settings. This should be added to the help page here, i suggest !!!)
However, on the German help page it says " Wir weisen Sie darauf hin, dass die Standard-Funktionalität von Filelink keine Verschlüsselung von Anhängen vorsieht." Which means, that the standard funcionallity of Filelink uses no encryption for the attachments. So while the English help refers to the standard e-mail with standard attachment, the German page refers to Filelink. I think this error was introduced in the translation.
However, I see clearly that the help page does not make clear the distinction between encryption during sending and encryption during the storage on the servers. Thats why the confusion comes from.
As a summary I would put it like this: (do you agree?)
Standard e-mails (including login data, e-mail text, standard attachment) are not encrypted by Thunderbird during sending to your e-mail provider unless in the settings "SSL/TLS" is chosen. Then at least the login data are encrypted during sending, but whether the e-mail text and standard attachments are also encrypted during sending depends on your e-mail provider. On the server of the e-mail providers all the data are not encrypted again, unless you use additional programmes to encrypt the e-mail text and standard attachments prior to sending. Filelink attachments always use HTTPS connections, which means that the attachments are encrypted by SSL/TLS during sending to the Filelink provider. On his server, the data are not encrypted any more unless you have encrypted the data with an additional programme before sending it. Which in the end means that Filelink is as secure or unsecure as standard Thunderbird e-mails with standard attachments when using the SSL/TLS option in the Thunderbird settings.
Ok. Thanks for clarification.
What I still don't understand is, why the encryption, which can be done by S/MIME or GPG is not included in Thunderbird, so that everyone can encrypt his e-mail easily without additional programmes before sending?