Additional info from https://support.mozilla.org/en-US/questions/1486309 Failed to inform in the initial message that we're talking six .mp4 files ranging from 26MB to 96MB. Hope this helps.

POSTER - Please do not begin new threads for the same problem. Post underneath your original post if you have additional info. Thanks.

See https://support.mozilla.org/en-US/kb/filelink-large-attachments

frisee -

"POSTER - Please do not begin new threads for the same problem. Post underneath your original post if you have additional info. Thanks."

Thank you for your response. I have no clue how to "post underneath [my] original post" . . .

sfhowes -

You sent a link. Attempting to understand all of the ins-and-outs of that lengthy discussion about Filelinks, I come to a ending point at:

"Adding Filelink To use this feature, you need to install one of the Filelink provider add-ons first, as described below. For some online storage service providers, you may have to first create a new account or configure an existing account with them. "

Great. I have over the years installed add-ons to TB, so am not completely ignorant. However, this "need to install one of the Filelink provider add-ons first" is entirely useless, since I have no clue what those are, what all the 1) " your Dropbox instead of sending them by email", 2) "Thunderbird's FileLink feature", 3) "Securely encrypt and upload large attachments to any Send service instance (formerly Firefox Send)", 4) "your WebDAV account instead of sending them by email" (same as "Dropbox" -- have no idea to what this is referring), 5) "cloud - FileLink for Nextcloud and ownCloud Featured" (whatever that means), 6) "your Box instead of sending them by email", 7) "your OwnCloud or NextCloud server and instead inserts a public link into your email", 8) "you can store attachments on a seafile share" . . . Eight wonderfully exciting things to do (I suppose) if one had any understanding what any of them are talking about.

Thank you nonetheless for your response.