I am trying to attach a PDF of just 5024KB to a mailing in CiviMail. The attachment is failing, with no explanation as to why. Is there a file size limit or could anyone suggest another reason a file would not attach? Many thanks.
You might also want to look at the upload_max_filesize directive in php.ini
SMTP providers have their own limits as to what attachments/file sizes they allow. For example - CiviSMTP (UAS) - has been max = 1MB for a long time. Not 100% if that has changed, but it makes sense that there are limits as to attachments to bulk email messages.