To make one sequence a reference sequence, just select its name from the gap4 Edit Contig window and right click and select as reference sequence. If the file is in embl format, the features will show up as Staden tags in the alignment.
KMail has always problems with multiple smtp servers. As a solution I installed sendmail. Then I just created a new outgoing mailserver and selected the sendmail option. No further configuration was necessary and it seems to work.
I am trying to use EMBOSS for the assembly of vector sequences. Long time ago, I used the CGC seqed program for this purpose and at the moment I use the Gene Construction Kit. EMBOSS doesn't have a straight equivalent for seqed and one has to use a bunch of other tools to replace its functionality. Look at this comparison between CGC and EMBOSS.