Problems with certified mail

Hi, I have been using your program for more than a year and I am fine, it has many integrated functions, such as the calendar which is very useful to me, however, in case I have a PEC of Aruba I have problems reading and downloading the attachments.
Let me explain better when I receive mail from my PEC I cannot regularly view the text of the email and not even the attachments, especially PDFs, which is very important as documents arrive.
What I see as attachments are:
daticert.xml, postacert.xml, smime.p7s but not PDF and not even the text of the email.
To read the PEC email I have to access either the PEC email portal or by accessing the traditional account without viewing it in Mail Bird.
Are you aware of this, or this is normal, because I, without using Mail Bird, so Gmail or Alice the PEC I see it regularly.
In thanking you in advance, I offer you my greetings.